After being released from prison for a brutal assault in which he too was a victim, Terry returns home to his mother's (Ann Sothern) boarding house. Unable to cope with his freedom and uncertain about how to appease his ever growing desire to harm those around him, Terry finds solace in playing violent practical jokes. But when an attractive young woman (Cindy Williams) moves into the boarding house, Terry finds himself overpowered by violent impulses and, in a fit of rage, accidentally murders the woman. Now engulfed by bloodlust, it's not long before he begins seeking out more victims...