When Susan was in school, she was popular with all the boys, but Harold became obsessed with her. On one Valentine's Day, when Susan turns him down in favor of David, Harold breaks into her house and kills David. Nineteen years later, Susan is a married woman who has put the murder largely out of her mind, but Harold has not forgotten her. When she goes to a local hospital for a checkup, she finds that someone there does not want her to leave, and that a killer disguised as a surgeon is stalking her while he murders or maims anyone who gets in his way. .