Goodwin announces a new ED Chief, and the choice doesn't make everyone happy; Dr. Manning takes a stand for her patient and finds herself dealing with the repercussions; Dr. Charles tends to family affairs.

The rookies are asked to develop their first confidential informants; Officer Chen's mother complicates her home life when she comes to stay with her.

The designers take on a Joe Fresh challenge, where each is assigned a timeless wardrobe staple to inspire a transformative look.

An emergency alert of an impending missile attack sends Los Angeles into chaos and uncertainty, while the officers each try to keep the peace and deal with their own disasters.

Police in Abbotsford, B.C. hunt a stalker who has left one teen dead and another barely alive.

They say fences make good neighbors, but sometimes they can make dead ones.

Phoenix police face a unique serial killer team that is stalking and killing innocent people.

Police discover a murdered teenage girl was involved in a love triangle.

When a girl calls 911, the dispatcher does not believe that an intruder has entered her house until gunshots are heard; upon arriving, the SRU discovers that the girl has been abducted.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

They say fences make good neighbors, but sometimes they can make dead ones.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

Phoenix police face a unique serial killer team that is stalking and killing innocent people.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

When a girl calls 911, the dispatcher does not believe that an intruder has entered her house until gunshots are heard; upon arriving, the SRU discovers that the girl has been abducted.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

They say fences make good neighbors, but sometimes they can make dead ones.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

When a girl calls 911, the dispatcher does not believe that an intruder has entered her house until gunshots are heard; upon arriving, the SRU discovers that the girl has been abducted.

The first responders take calls involving an unusual domestic disturbance, a "death" at a psychic's place, and a motorcycle crash; Bobby dips his toes into the dating pool; Abby walks down memory lane, and Buck is confronted by his past actions.

Hayley is shocked by the arrival of a new client at the firm; the Hawthornes struggle to repair a broken connection; Vanessa receives an intriguing business proposition; Shanice offers Ted some food and friendship; Kat has to answer tough questions.

On one of the hottest days of the year, the first responders must deal with harrowing incidents all around the city; Buck gets a surprise visit from his sister; Athena questions her relationship with Bobby; Buck worries about a handsome new hire.

Lena's pursuit of justice forces Danny into an unexpected role reversal; Sarah faces a personal dilemma that tests her resolve; Mae contends with political pressure; Sean and Jonah uncover more than they anticipated during a routine case.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

Sgt. Gray informs the rookies that they must track down a specific set of crimes in a 48-hour period to qualify for their final exam; Nolan and Bishop answer a silent alarm call at will.i.am's house.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

As the rookies prepare for a big exam to see who moves on to the next stage of training, Nolan and Bishop are called to the scene of a murder and learn that the victim may be tied to a potential terrorist attack on the city of Los Angeles.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

The officers grapple with the aftermath of a plotted attack on the city of Los Angeles, leaving Bradford fighting for his life.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

Nolan teams up with new night detective Pablo Armstrong for a murder investigation case that results in an unexpected reunion with a former love interest.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

Lena's pursuit of justice forces Danny into an unexpected role reversal; Sarah faces a personal dilemma that tests her resolve; Mae contends with political pressure; Sean and Jonah uncover more than they anticipated during a routine case.

The first responders take calls involving an unusual domestic disturbance, a "death" at a psychic's place, and a motorcycle crash; Bobby dips his toes into the dating pool; Abby walks down memory lane, and Buck is confronted by his past actions.

When a grieving mother becomes the prime suspect in her missing daughter's murder, Colter sets out to find the true culprit and prove her innocence.

On one of the hottest days of the year, the first responders must deal with harrowing incidents all around the city; Buck gets a surprise visit from his sister; Athena questions her relationship with Bobby; Buck worries about a handsome new hire.

Officer Nolan navigates his relationship with Jessica and a developing rapport with Grace while working a high-stakes criminal case involving an undercover homeland security agent; Officer Chen meddles with Officer Bradford's love life.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

Sgt. Gray informs the rookies that they must track down a specific set of crimes in a 48-hour period to qualify for their final exam; Nolan and Bishop answer a silent alarm call at will.i.am's house.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

When a grieving mother becomes the prime suspect in her missing daughter's murder, Colter sets out to find the true culprit and prove her innocence.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

The officers grapple with the aftermath of a plotted attack on the city of Los Angeles, leaving Bradford fighting for his life.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

Nolan teams up with new night detective Pablo Armstrong for a murder investigation case that results in an unexpected reunion with a former love interest.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

Officer Nolan gets off to a rocky start after being introduced to his new training officer; Officer Bradford struggles to think of an appropriate birthday gift for Rachel; Officer Lopez finds herself navigating a case that triggers a personal memory.

Police in Abbotsford, B.C. hunt a stalker who has left one teen dead and another barely alive.

The rookies are asked to develop their first confidential informants; Officer Chen's mother complicates her home life when she comes to stay with her.

An emergency alert of an impending missile attack sends Los Angeles into chaos and uncertainty, while the officers each try to keep the peace and deal with their own disasters.

A killer who leaves messages signed "Jack" terrorizes East Point, Ga.

Police in Abbotsford, B.C. hunt a stalker who has left one teen dead and another barely alive.

Todd Kendhammer claims his wife was killed in a freak car accident but the forensic evidence doesn't back him up.

A killer who leaves messages signed "Jack" terrorizes East Point, Ga.

When Leslie Neulander's death is declared accidental, forensic investigators sound the alarm that it was no accident.

Police discover a murdered teenage girl was involved in a love triangle.

A suitcase filled with unidentified human remains unlocks a missing person's case that has gone unsolved for years; the forensic analysis of a nearly-destroyed cellphone found in the suitcase reveals a mysterious selfie.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

The first responders take calls involving an unusual domestic disturbance, a "death" at a psychic's place, and a motorcycle crash; Bobby dips his toes into the dating pool; Abby walks down memory lane, and Buck is confronted by his past actions.

Boden is on edge after starting a new fad diet; Casey and Severide disagree on a call; Brett's birth mother shares life-altering news; a familiar face has a proposition for Herrmann.

On one of the hottest days of the year, the first responders must deal with harrowing incidents all around the city; Buck gets a surprise visit from his sister; Athena questions her relationship with Bobby; Buck worries about a handsome new hire.

Things get personal for Casey and Gallo in the aftermath of a suburban house fire involving a mother and her young son; Herrmann campaigns for more respect; Kidd has an idea for giving back to her community.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

The first responders take calls involving an unusual domestic disturbance, a "death" at a psychic's place, and a motorcycle crash; Bobby dips his toes into the dating pool; Abby walks down memory lane, and Buck is confronted by his past actions.

Boden is on edge after starting a new fad diet; Casey and Severide disagree on a call; Brett's birth mother shares life-altering news; a familiar face has a proposition for Herrmann.

On one of the hottest days of the year, the first responders must deal with harrowing incidents all around the city; Buck gets a surprise visit from his sister; Athena questions her relationship with Bobby; Buck worries about a handsome new hire.

Things get personal for Casey and Gallo in the aftermath of a suburban house fire involving a mother and her young son; Herrmann campaigns for more respect; Kidd has an idea for giving back to her community.

The crew races to an emergency at an Indian wedding; Abby enlists Buck to help her find her mother; Abby meets Athena for the first time; Bobby confronts his past; Hen struggles to make the right decision.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

On Valentine's Day, a surprise marriage proposal goes awry with dangerous consequences; Athena attempts to help a desperate woman; Bobby and Chimney pull holiday duty; Abby and Buck go on their first official date.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

A full moon keeps the crew busy with crazy calls; Athena investigates a potential home invasion; Abby helps investigate a caller's murder; Bobby and Buck have their hands full at a yoga studio for pregnant women; Hen's past may become her future.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

Bobby gets a surprising phone call from his doctor after donating at Chimney's blood drive; Athena confronts Michael after having a heart-to-heart with their kids.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

The first responders race to help a homeless man crushed in a garbage truck, a mother and son in a crashed elevator, and extreme hoarders trapped in their house; Athena starts dating; the situation with Abby's mother tests her relationship with Buck.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

Police in Abbotsford, B.C. hunt a stalker who has left one teen dead and another barely alive.

Todd Kendhammer claims his wife was killed in a freak car accident but the forensic evidence doesn't back him up.

A killer who leaves messages signed "Jack" terrorizes East Point, Ga.

Some grudges die hard, but this neighbor's won't die until his enemies do.

Todd Kendhammer claims his wife was killed in a freak car accident but the forensic evidence doesn't back him up.

When Leslie Neulander's death is declared accidental, forensic investigators sound the alarm that it was no accident.

A suitcase filled with unidentified human remains unlocks a missing person's case that has gone unsolved for years; the forensic analysis of a nearly-destroyed cellphone found in the suitcase reveals a mysterious selfie.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

Some grudges die hard, but this neighbor's won't die until his enemies do.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

When Lanell Barsock is found murdered, it seems obvious to all that her boyfriend did it; when the forensic evidence comes in, investigators are astonished to learn they've arrested the wrong person.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

Some grudges die hard, but this neighbor's won't die until his enemies do.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

Boden is on edge after starting a new fad diet; Casey and Severide disagree on a call; Brett's birth mother shares life-altering news; a familiar face has a proposition for Herrmann.

Anita receives a call that leaves her shaken; a meeting between Hayley and a new client at the firm hints at a shared past; Bill receives an unexpected proposal about his future from Joey; Vernon seeks out Andre's help.

Things get personal for Casey and Gallo in the aftermath of a suburban house fire involving a mother and her young son; Herrmann campaigns for more respect; Kidd has an idea for giving back to her community.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

Boden is on edge after starting a new fad diet; Casey and Severide disagree on a call; Brett's birth mother shares life-altering news; a familiar face has a proposition for Herrmann.

Things get personal for Casey and Gallo in the aftermath of a suburban house fire involving a mother and her young son; Herrmann campaigns for more respect; Kidd has an idea for giving back to her community.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20; all under the same roof, Casey clashes with Capt. Delaney, while Foster, Kidd and Brett fear Capt. Leone has it out for them; Boden mulls a procedural overhaul.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

While completing a task assigned by headquarters, Boden makes an unforeseen connection; Gallo is forced to make a surprise rescue of one of their own when the firehouse is called to the site of a construction explosion; Mouch reignites an old feud.

Todd Kendhammer claims his wife was killed in a freak car accident but the forensic evidence doesn't back him up.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.

When Leslie Neulander's death is declared accidental, forensic investigators sound the alarm that it was no accident.

Some grudges die hard, but this neighbor's won't die until his enemies do.

When Lanell Barsock is found murdered, it seems obvious to all that her boyfriend did it; when the forensic evidence comes in, investigators are astonished to learn they've arrested the wrong person.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

Some grudges die hard, but this neighbor's won't die until his enemies do.

When Lanell Barsock is found murdered, it seems obvious to all that her boyfriend did it; when the forensic evidence comes in, investigators are astonished to learn they've arrested the wrong person.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

Some grudges die hard, but this neighbor's won't die until his enemies do.

The team's actions, particularly Sgt. Parker's, are called into question after a shooting at a museum gala.

Anita receives a call that leaves her shaken; a meeting between Hayley and a new client at the firm hints at a shared past; Bill receives an unexpected proposal about his future from Joey; Vernon seeks out Andre's help.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.

Dr. Rhodes cares for Dr. Downey while Goodwin deals with personal issues; April gets hit while tending to a disorderly patient; Dr. Manning's past starts to catch up with her.

Tension builds when a group of rabble-rousers attempts to lock down the firehouse; Brett is faced with a monumental decision; Cruz readies himself for a big day; Gallo and Ritter attempt to launch Firehouse 51 into the social media age.

Dr. Rhodes begins his cardiothoracic surgery fellowship but gets off on the wrong foot with his new boss; Dr. Choi begins his life as chief resident; Sarah is caught off-guard by Dr. Charles; April tries to deal with her recently discovered illness.

When one of 51's own gets injured on a call, Severide becomes obsessed with helping out; Foster contemplates a big decision; Kidd is concerned for one of her high school trainees.

Dr. Manning and Dr. Rhodes suspect that two separate cases involving sick babies may be connected; a homeless patient's upbeat disposition enlightens Dr. Halstead and Dr.Charles; Dr. Choi and a Navy corpsman deal with the toll of gang violence.

As Firehouse 51 welcomes a new member to the team, whose presence could provide some complications, Brett's leadership shines during a scary call; Boden sees great potential in Kidd and proposes an idea that could have lasting repercussions.

An Indonesian man who doesn't speak English arrives at the hospital with a mysterious illness; Dr. Halstead attends Maggie's family reunion; Dr. Rhodes accepts a complicated heart surgery without consulting Dr. Latham.

Brett and Mackey find their lives in peril; Casey and Brett tread in unfamiliar territory; Severide chases a memory while Kidd adeptly solves a firehouse problem; Ritter puts himself in harm's way during a harrowing call.

When several patients turn out to have the same rare infection, Dr. Charles' epidemiologist daughter comes in to consult; an elderly patient's son and young girlfriend disagree over his treatment; Dr. Reese tries to help a young drug addict.

A mishap on the aerial ladder in the midst of a fire rescue leaves Mouch shaken and questioning his abilities; Kidd looks for support from Severide while Casey and Brett discuss their future.

A car crash at the Chicago Marathon leaves victims in critical condition; April and her medical resident brother must perform an intense operation in the field; an 8-year-old girl experiences sudden hearing loss; Dr. Choi treats a malnourished woman.

While completing a task assigned by headquarters, Boden makes an unforeseen connection; Gallo is forced to make a surprise rescue of one of their own when the firehouse is called to the site of a construction explosion; Mouch reignites an old feud.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.

Dr. Rhodes cares for Dr. Downey while Goodwin deals with personal issues; April gets hit while tending to a disorderly patient; Dr. Manning's past starts to catch up with her.

Tension builds when a group of rabble-rousers attempts to lock down the firehouse; Brett is faced with a monumental decision; Cruz readies himself for a big day; Gallo and Ritter attempt to launch Firehouse 51 into the social media age.

Dr. Rhodes begins his cardiothoracic surgery fellowship but gets off on the wrong foot with his new boss; Dr. Choi begins his life as chief resident; Sarah is caught off-guard by Dr. Charles; April tries to deal with her recently discovered illness.

When one of 51's own gets injured on a call, Severide becomes obsessed with helping out; Foster contemplates a big decision; Kidd is concerned for one of her high school trainees.

Dr. Manning and Dr. Rhodes suspect that two separate cases involving sick babies may be connected; a homeless patient's upbeat disposition enlightens Dr. Halstead and Dr.Charles; Dr. Choi and a Navy corpsman deal with the toll of gang violence.

As Firehouse 51 welcomes a new member to the team, whose presence could provide some complications, Brett's leadership shines during a scary call; Boden sees great potential in Kidd and proposes an idea that could have lasting repercussions.

An Indonesian man who doesn't speak English arrives at the hospital with a mysterious illness; Dr. Halstead attends Maggie's family reunion; Dr. Rhodes accepts a complicated heart surgery without consulting Dr. Latham.

Brett and Mackey find their lives in peril; Casey and Brett tread in unfamiliar territory; Severide chases a memory while Kidd adeptly solves a firehouse problem; Ritter puts himself in harm's way during a harrowing call.

When several patients turn out to have the same rare infection, Dr. Charles' epidemiologist daughter comes in to consult; an elderly patient's son and young girlfriend disagree over his treatment; Dr. Reese tries to help a young drug addict.

A mishap on the aerial ladder in the midst of a fire rescue leaves Mouch shaken and questioning his abilities; Kidd looks for support from Severide while Casey and Brett discuss their future.

A car crash at the Chicago Marathon leaves victims in critical condition; April and her medical resident brother must perform an intense operation in the field; an 8-year-old girl experiences sudden hearing loss; Dr. Choi treats a malnourished woman.

While completing a task assigned by headquarters, Boden makes an unforeseen connection; Gallo is forced to make a surprise rescue of one of their own when the firehouse is called to the site of a construction explosion; Mouch reignites an old feud.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.

A Virginia man insists, What's mine is mine, and what's yours is mine.

Homicide investigators are convinced an apparent murder-suicide was staged but the experienced CSI on the scene disagrees; only the instincts of the cops, coupled with an outside forensic expert's opinion, convince authorities who the real killer is.

Spike discovers his former mentor may be implicated in a tangled case involving corruption, drug dealers and an attempted gang execution.

A Virginia man insists, What's mine is mine, and what's yours is mine.

Homicide investigators are convinced an apparent murder-suicide was staged but the experienced CSI on the scene disagrees; only the instincts of the cops, coupled with an outside forensic expert's opinion, convince authorities who the real killer is.

Spike discovers his former mentor may be implicated in a tangled case involving corruption, drug dealers and an attempted gang execution.

A Virginia man insists, What's mine is mine, and what's yours is mine.

Spike discovers his former mentor may be implicated in a tangled case involving corruption, drug dealers and an attempted gang execution.

Anita keeps a secret from her family; Vanessa drops an emotional bombshell on Joey; Dani catches someone snooping in her home; Kat and Tomas disagree about what's best for his future.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.

Dr. Rhodes cares for Dr. Downey while Goodwin deals with personal issues; April gets hit while tending to a disorderly patient; Dr. Manning's past starts to catch up with her.

Dr. Rhodes begins his cardiothoracic surgery fellowship but gets off on the wrong foot with his new boss; Dr. Choi begins his life as chief resident; Sarah is caught off-guard by Dr. Charles; April tries to deal with her recently discovered illness.

Dr. Manning and Dr. Rhodes suspect that two separate cases involving sick babies may be connected; a homeless patient's upbeat disposition enlightens Dr. Halstead and Dr.Charles; Dr. Choi and a Navy corpsman deal with the toll of gang violence.

An Indonesian man who doesn't speak English arrives at the hospital with a mysterious illness; Dr. Halstead attends Maggie's family reunion; Dr. Rhodes accepts a complicated heart surgery without consulting Dr. Latham.

When several patients turn out to have the same rare infection, Dr. Charles' epidemiologist daughter comes in to consult; an elderly patient's son and young girlfriend disagree over his treatment; Dr. Reese tries to help a young drug addict.

A car crash at the Chicago Marathon leaves victims in critical condition; April and her medical resident brother must perform an intense operation in the field; an 8-year-old girl experiences sudden hearing loss; Dr. Choi treats a malnourished woman.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.

Dr. Rhodes cares for Dr. Downey while Goodwin deals with personal issues; April gets hit while tending to a disorderly patient; Dr. Manning's past starts to catch up with her.

Dr. Rhodes begins his cardiothoracic surgery fellowship but gets off on the wrong foot with his new boss; Dr. Choi begins his life as chief resident; Sarah is caught off-guard by Dr. Charles; April tries to deal with her recently discovered illness.

Dr. Manning and Dr. Rhodes suspect that two separate cases involving sick babies may be connected; a homeless patient's upbeat disposition enlightens Dr. Halstead and Dr.Charles; Dr. Choi and a Navy corpsman deal with the toll of gang violence.

An Indonesian man who doesn't speak English arrives at the hospital with a mysterious illness; Dr. Halstead attends Maggie's family reunion; Dr. Rhodes accepts a complicated heart surgery without consulting Dr. Latham.

When several patients turn out to have the same rare infection, Dr. Charles' epidemiologist daughter comes in to consult; an elderly patient's son and young girlfriend disagree over his treatment; Dr. Reese tries to help a young drug addict.

A car crash at the Chicago Marathon leaves victims in critical condition; April and her medical resident brother must perform an intense operation in the field; an 8-year-old girl experiences sudden hearing loss; Dr. Choi treats a malnourished woman.

Dr. Charles and April team up to take on a mysterious patient in the ED; Dr. Halstead is forced to make a life-or-death decision for one of his trial patients; Dr. Marcel is confronted by his past when a former acquaintance is brought into the ED.