Feeling unwanted and unloved by his flirtatious mother and his weak, alcoholic father, shy teenager Craig Fowler becomes a masked prowler, finding vicarious pleasure in spying upon the private activities of neighbors in a modern suburban area. Though he is caught in the act of spying upon his next-door neighbors, the unhappily married Lowells, his identity remains unknown, and the police begin to take an active interest in the case. Following a quarrel, Craig's mother, Jackie, storms out of the house and goes off with the promiscuous Gareth Lowell. Craig then begins drinking, visits the Lowell daughter, Eileen, and attempts to seduce her. In resisting, she trips and falls through a glass-topped table, and is knocked unconscious. Panic-stricken, Craig flees from the scene. Later, at a pool party, Jay Fowler catches his wife making love to Gareth, and the resulting fight ends abruptly when the masked prowler is spotted on a patio roof. Craig attempts to get away, but he is caught by a plainclothesman. The incident has a sobering effect upon his parents, who resolve to provide a healthier home life for their son.