An experiment to transplant limbs on a wounded Vietnam Veteran leads to a monster being unleashed in Los Angeles.
Dr. Stein is in his laboratory. Winifred Walker lands at the Hollywood-Burbank Airport and drives a car to Dr. Stein's laboratory. Malcomb answers the door and has her wait while he gets Dr. Stein. Malcomb brings her into Dr. Stein's lab and she tells him about her fiance, Eddie Turner, who was injured by a landmine in Vietnam. At dinner, Dr. Stein and Winifred discuss his work and she asks him if maybe he can help Eddie. Dr. Stein agrees to try and help and suggests Winifred look around his laboratory. On their way to the Veterans Affairs hospital, Winifred tells Dr. Stein that Eddie lost all of his limbs. They are greeted by the Hospital Receptionist and tell her they are looking for Eddie Turner. The Hospital Receptionist asks the Hospital Supervisor and she tells them he is in Ward 5. Eddie Turner is in bed when the Hospital Attendant comes into his room. Eddie asks for ice cream and the Hospital Attendant tells him he doesn't have time to be giving him and the others special attention just because they were wounded in Vietnam. He then tells Eddie that his friends had a party for him when his draft lottery number was called, but he then had to go back and tell his friends he had been rejected for service for having a bad heart. The Hospital Attendant then criticizes Eddie for going to Vietnam and tells him, he and his friends' tax dollars will have to pay for his care. Winifred and Dr. Stein go into Eddie's room and Winifred introduces Dr. Stein to Eddie. She and Dr. Stein then offer to help Eddie and he is taken to Dr. Stein's lab.
Eddie is given his first dose of DNA in preparation for his surgery. Dr. Stein introduces Winifred to Eleanor who is taking injections to reduce the effects of aging on her looks. He tells Winifred part of their work will be trying to figure out how to make the DNA stick so people like Eleanor wont constantly have to have injections. He then takes her to see Bruno Stragor who had two legs grafted on to his body. Dr. Stein then shows her one of Bruno's legs that is striped like a tiger due to an RNA rejection. Eddie has new limbs grafted onto him and the operation is a success. During the night Bruno starts screaming and Dr. Stein, Winifred, and Malcomb are forced to put him into a straight jacket and Dr. Stein tells Winifred the side effect of the injections can lead to sudden states like Bruno is experiencing. Eddie's bandages are removed and he is able to feel when Dr. Stein touches his finger. Malcomb tells Winifred that he is love with her, but she tells him she loves Eddie. Later, Malcomb switches the DNA from Bruno's bottle into Eddie's bottle. Eddie is brought into the surgery room for the final stage of his operation and he is given the DNA meant for Bruno. At dinner, Dr. Stein tells Winifred that Eddie should be walking on his own today and when Winifred becomes excited, Malcomb frowns. Winifred and Dr. Stein visit Eddie and Winifred notices Eddie growing a large brow ridge. They visit Eddie later, but he shows no signs of improving and is starting to grow hair in odd patches.
During the night, Eddie gets free and walks out of the lab. He walks to the VA hospital and strangles the Hospital Attendant and rips off his arm, which Eddie then eats. A Couple in Bed are making love when the woman hears her dog barking. The Man goes outside to check what the dog is barking about and he is killed by Eddie, who then kills the woman and eats her guts and returning to the lab. Winifred checks on the DNA and starts to figure out that something could be wrong with the solution Eddie is getting. During the night, Eddie gets up again and leaves the lab. He goes to a park where there is a Couple in Car parked. The man starts to fondle the woman's hair and she asks him to take her home. He tries to touch her leg and she gets out of the car and starts walking in the park. Eddie follows her and then drags her and kills her and returns to the lab. The next day, Eddie attacks Dr. Stein, but he manages to get away. Police Sgt. "Jackson" and a Police Lieutenant arrive at the lab and ask Dr. Stein if he has seen anything unusual and tells him about the murders.
Eddie leaves the lab again and heads towards the Parisian Room where he kills a woman outside. A Nightclub Comedian tells jokes about not being served at a diner and a man with a talking dog. The Nightclub Comedian then introduces the Nightclub Singer who starts to sing. The Nightclub Comedian goes outside to have a cigarette and sees Eddie kill a Couple in Alley and then eat the woman's guts. The Nightclub Comedian then tells Sergeant Jackson about what he saw. Eddie goes back to the lab as Malcomb is attempting to rape Winifred. Eddie breaks into the room and kills Malcomb. Winifred tells Dr. Stein, the monster is Eddie. Eddie walks into Bruno's room and they fight until Eddie breaks Bruno's back. Eddie also kills Eleanor at the top of the stairs. As Eddie is walking towards Winifred, she calls his name and he walks away. Dr. Stein attacks Eddie and Eddie strangles him. Eddie then attacks a Girl in Dune Buggy. Sergeant Jackson and Police Lieutenant arrive at the lab and help Winifred. Eddie carries the Girl in Dune Buggy inside of a warehouse, and she manages to run away. As she is climbing up a ladder, the Girl in Dune Buggy is grabbed by Eddie and killed. The Los Angeles County Canine Corps arrives and three doberman's are released. They then attack and kill Eddie after ripping his newly attached limbs off. Sergeant Jackson then comforts Winifred.