Karl Childers, now a grown man, is released from a psychiatric hospital where he has been hospitalized since the age of 12 for the murder of his mother and her lover. He returns to his childhood town and although being mentally handicapped, gets a job fixing small motors at a local repair shop. Karl befriends a young boy, Frank, and is soon invited by Frank's mother, Linda, to move into the family's garage. As a strong relationship develops between Karl and Frank, a confrontation builds with Linda's abusive and sometimes violent boyfriend Doyle.
