After escaping a Puget Sound institution, "Stepfather" Gene Clifford alters his appearance with plastic surgery and takes on another new identity: Keith Grant. Moving to Deer View, California, Keith falls for a divorced school principal, arousing the suspicions of her wheelchair-bound, computer-savvy son.
A disturbed boy kills his father with his farm tractor and his arm is mangled in the process. He's taken to a mental hospital where he's outfitted with a hook to replace his lost hand and, years later, he's eventually released from the asylum. He returns home to find his mother has remarried, which sets him off on a murderous rampage.
Trapped in a cave, five men cut the arm off of another companion in order to ward off starvation. After they are saved, their victim seeks revenge on them one by one.
