Professor Frankenstein (Whit Bissell), a guest lecturer from England, talks Dr. Karlton (Robert Burton), into becoming am unwilling accomplice in his secret plan to actually assemble a human being from the parts of different cadavers. After the recovery of a body from a dreadful automobile wreck, Professor Frankenstein takes the body to his laboratory-morgue, where in various drawers he keeps spare parts of human beings. The Professor also enlists the aid of Margaret (Phyllis Coates), as his secretary to keep all callers away from the laboratory. Margaret, becoming suspicious of what is going on decides to investigate and goes down to the morgue. She is panic-stricken by this horrible monster who has been activated by electricity following the grafting of a new leg and arm. She dares not tell the Professor about her feelings, and keeps silent for the present.
Professor Frankenstein teaches the Monster (Gary Conway) to talk,and one night the Monster steals out of the laboratory and goes on a rampage when frightened by the sounds of street noises. He breaks into a girl's room, the girl becomes hysterical and starts screaming, and in his attempt to silence her, he kills her in panic and flees. The next morning the hunt for the murderer is on. Margaret, angry at the Professor, tells him that she knows about the Monster that did the murder. The Professor, taking no chances, has the Monster kill her and feeds her remains to a crocodile. Dr. Karlton, sent out of town, knows none of this. The Professor sends the Monster to a Lover's Lane, where he kills a teenager. The face of the teenager is successfully transferred to the Monster. Professor Frankenstein tells Dr. Karlton of his plans to dismember his creation and ship him in various boxes to England -- there to put him together again. When they strap the Monster down again, he becmes suspicious and tears loose to throw Dr. Frankenstein into the crocodile pit, while Dr. Karlton runs for help. When Dr. Karlton arrives with the police, the Monster who is maddened with fright, backs into the electrical dial board. Contact with the iron wrist bands electrocutes him and his handsome face disappears and the bruised gruesome original head appears.