At Brattle Press, publisher Willard I. Whitcombe learns that Steven Kenet, a former bomber pilot and the husband of his secretary, Helen, has returned home after a two-year absence and followed Helen to Whitcombe's apartment, where she has gone to pick up a manuscript. At the same time, Steven, who now has the body of his dead wife in his car, drives into a shallow river, attempting to kill himself. He is stopped, however, by the police, who determine that because of recent brain surgery, Steven, who has no memory of Helen's death, needs a psychological exam. At the Hamblin County Psychiatric Hospital, when the police hand Steven his war medal and a photograph of him with his son, the six-year-old Richard, Steven becomes despondent. Soon after, the doctors at the hospital, including Dr. Ann Lorrison, observe a blood clot in Steven's brain and note that such clots can cause emotional and physical changes and memory loss. When Steven will not consent to surgical removal of the clot, Assistant District Attorney David Wallace guesses that Steven wants to use his infirmity as a defense in his murder trial, and insists that the doctors ask Steven's mother for her consent. Ann and Wallace go to Steven's house, but find his mother dead and Richard alone and in shock. Although Ann gains temporary custody of Richard, she tells Steven that his son will go to a county orphanage unless he has the operation, which will allow him to be judged sane and gain control of his finances. Steven agrees to the surgery, which indeed cures him, but fails to restore his memory of what happened the night Helen died. Although he is permitted to visit Richard, he refuses, out of fear of facing the boy. While Steven is undergoing the final tests before being released to the court, Whitcombe is rebuffing blackmail attempts by his elevator operator, Henry Cronner, who knows how Helen died. When Cronner offers the information to Steven instead, Whitcombe kills him before he can divulge the information. Cronner's offer, however, has made Steven realize that regaining his memory might prove his innocence, so he takes a truth serum, sodium pentothol, from Ann and recounts the events of the evening of Helen's death: On the night that she died, Steven finds her at Whitcombe's house, clearly having an affair with her boss, and starts to attack her out of jealousy but blacks out and wakens to find her dead. Back in the present, Ann watches Steven fall asleep, and is startled when she later finds him hiding in her car. Steven forces her to drive him to Whitcombe's, where he re-enacts the murder night's activities. He also remembers seeing a suitcase there that night, but notes that it had been removed by the time he awakened, suggesting that someone else had been in the room. Ann decides not to turn Steven in, and they leave the apartment looking just as it did that night, causing Whitcombe to panic when he comes home. After receiving word that he has been made a partner in his firm, Whitcombe visits Steven and baits him into attacking him by telling him that he killed Cronner and Helen. As a result of the attack, Steven is placed in permanent seclusion. When Ann visits him, Steven tells her what has happened, grabs her keys and escapes to prove his innocence, prompting a city-wide manhunt. The next day, Ann finds him outside Whitcombe's apartment and tells him she loves him. Together they trap Whitcombe, inject him with sodium pentathol and convince the police to listen as Whitcombe confesses that he murdered Helen, who threatened to ruin him if he did not marry her. Later Ann brings Steven, whose name is now cleared, home to see Richard, and they embrace.