Jame Reese is a U.S. soldier stationed in Europe whose violent temper has sent him to the stockade several times. He is surprised one day to be driven to a remote hospital facility and checked into a room with another soldier named Miles. James learns that his roommate also has spells of aggressive

In West Germany, after being released from a U.S. stockade, Pvt. James Reese attends a birthday party for his girl friend Lisa. There, the mercurial Reese assaults one of the women guests and threatens her boyfriend when he objects. Later, as Lisa and Reese lie in bed discussing his belligerent behavior, several MPs arrive to arrest him for accosting the woman at the party. When Reese tries to resist, the MPs break his arm and take him to the hospital prison ward for observation. There, with his cell bugged, Reese is observed by Dr. Frederick and an army Major, who are recruiting subjects for Frederick's experiment on curbing sociopathic impulses. Deciding that Reese fits the profile, they have him shipped to a sanitarium in the country where he is greeted by Lawrence Shannon, the head orderly. Reese is quartered in a room with Lt. Tommy Rhodes, a catatonic black officer whose head is wrapped in bandages, and Sgt. Boford Miles, a Southern country boy who papers the wall over his bed with photos of pin-ups. As Rhodes howls in pain, Miles explains that the lieutenant is dying from stomach cancer and that he himself is dying from lung cancer. When Frederick enters the room to administer a narcotic to dull Rhodes's pain, Reese tries to question him, but the doctor dismisses his queries. That night, while exploring the sanitarium, Reese comes upon a room containing a caged monkey, his head wrapped in bandages, climbing the sides of his cage in distress. Upon returning to his room, Reese finds Miles leering though a pair of binoculars at a nurse undressing. The next day, Frederick and the Major meet with members of Congress who have been funding the project and are now impatient for Frederick's results. In the yard outside, Reese wanders into the woods and is puzzled to discover that the area is patrolled by guard dogs and fenced in by barbed wire. Later, after they see Shannon and Nurse Schroeder wheeling Rhodes away to the operating room on a stretcher, Reese wonders why Frederick is operating on Rhodes' brain to cure his stomach. When Reese asks Frederick why he has been confined to a ward with terminal patients, the doctor explains that he operated on Rhodes's brain in an experiment to stop pain at its source, then adds that Rhodes died on the operating table. Frederick defends his actions by stating that he plans to turn Rhodes's death into something meaningful by finding a treatment for schizophrenia. One day, Anna Kraus, a Red Cross nurse, comes to play checkers with Miles. When Anna kindly offers Reese some cookies, he feels patronized and lashes out at her, making her cry. Now alone with Anna, Miles, who has strong sexual urges, begins to fondle her, and when she begs him to stop and pushes him away, he becomes agitated and brutally rapes her. When Reese returns to his room, he finds Miles calmly reading a comic book. Sensing that Miles has raped Anna, Reese begins to taunt him about it. Miles, who veers between mania and morose depression, becomes enraged and attacks Reese. As the two wrestle on the ground, Miles begins to spit blood, prompting Reese to summon Shannon. Frederick, after examining Miles, diagnoses that he will die within six months, then proposes that the sergeant undergo brain surgery. When Miles demurs, Frederick asks about "Benson," a name Miles has frequently called out in his sleep. Miles confides that Benson served with him in combat, and that when a live grenade landed in their foxhole, Miles pushed Benson on top of it to spare himself. To persuade Miles to agree to surgery, Frederick suggests that by sacrificing himself for the betterment of mankind, Miles will compensate for killing Benson. After implanting a wire into Miles's brain, Frederick attaches feeder wires to the probes coming out of Miles's skull and hands him a button, which when pushed, will activate the circuit. Although Miles is afraid of the results, he pushes the button and is rewarded with a powerful orgasm. Becoming addicted to sexual gratification, Miles continually pushes the button, forgoing sleep and food for sex. When Reese comes to visit Miles, he is appalled by his condition and angrily throws Frederick to the floor. Reese then pulls the probes out of Miles's head, after which Miles keeps pushing the button and squalls like a baby when he receives no response. Furious that Reese is interfering with his project, the Major orders Shannon to confine Reese to his room. Reese smashes the door into Shannon and escapes, but is soon cornered by the guard dogs and captured by Shannon. After Miles dies, the Major pressures Frederick into operating on Reese. Trying to maintain his morality, Frederick refuses unless Reese will consent to the procedure. Soon after, Reese, his head swathed in bandages from the surgery, is given a probe to push. When Reese protests that he never volunteered for the operation, the Major reveals that he tricked Reese into signing the consent form by attaching it to the sheaf of papers he was required to sign upon admittance. When Frederick justifies the surgery by stating that Reese needed treatment for his violent, anti-social behavior, Reese retorts that his behavior defines his uniqueness and is not a disease. Refusing to push the button, Reese challenges Frederick to push it himself, and when the doctor hesitates, the Major grabs the button and presses it, sending Reese falling to the floor with a jolt. Some time later, Frederick and the Major return from Washington, D.C. after presenting Reese, their model patient, to the Congressional committee. The Major, who is soon to be promoted to colonel, introduces Reese at a press conference and explains that before surgery, Reese was a violent, helpless schizophrenic. When a reporter asks Reese how he feels now, Reese, in a zombie-like state, mechanically presses the button and flatly states, "I feel fine, just fine." The major then boasts that every stage of the experiment was a resounding success, and that no fatalities were suffered in the course of the research.