American tourists David and Jack are savaged by an unidentified vicious animal whilst hiking on the Yorkshire Moors. Retiring to the home of a beautiful nurse to recuperate, David soon experiences disturbing changes to his mind and body.

American tourists David and Jack are savaged by an unidentified vicious animal whilst hiking on the Yorkshire Moors. Retiring to the home of a beautiful nurse to recuperate, David soon experiences disturbing changes to his mind and body.