Divorcee Susan Jeremy goes to a local Los Angeles county hospital for a routine exam and through a series of circumstances finds herself stranded there while a maniac, dressed in a doctor's surgical mask and clothing, goes around killing all the staff are assoicated with her. Could it be posibly the psycho Harold whom killed a friend of Susan's on Valentine's Day 19 years earlier? If so, who is it since Susan has not seen Harold for all that time and there's no telling who he has grown up to look like.