A woman fights to intercept a letter in which her husband tries to prove her guilty of murder.

Housewife Ellen Jones worries about her husband George, who has changed dramatically since being bedridden with a heart condition, and wonders if the tempermental and depressed George will ever return to his former self. Although George, a former Air Force pilot who married Ellen during World War II, is quite ill, he exaggerates his symptoms and accuses her and his best friend, Dr. Ranney Grahame of not helping him. Unknown to either Ran or Ellen, George is secretly writing a letter to the district attorney, warning that Ellen and Ran are trying to kill him. When he has a brief attack, George begs Ellen to get another doctor, but because George has treated all of the other doctors so badly, only Ran will come. Despite George's accusation that Ellen deliberately delayed calling a doctor, Ran dismisses his concerns and suggests that he might want to consult a psychiatrist to help him avoid the morbid thoughts with which he is preoccupied. Later, when Ran and Ellen are alone, he tells her that George must go to the hospital to prevent his depression from worsening. She is distraught, knowing that George only wants her to attend him and seems to take violent dislikes to other people, but promises to talk to George. After chatting outside with Billy, a friendly neighborhood child who dresses like television cowboy Hopalong Cassidy, Ellen is startled to see George at the window. George denies having gotten out of bed, then accuses her of being in love with Ran and wanting him dead. Although hurt, Ellen believes the illness is making George so distrustful, and goes downstairs to make his lunch. As soon as Ellen leaves the room, George continues his letter, embellishing it with details that further incriminate Ellen. After lunch, George says that he is feeling better and asks Ellen to mail a letter that contains some insurance papers he has worked on for his office. Because Mr. Carston, the mailman to whom Ellen gives the letter, has seen George at the window, Ellen immediately goes to his room and begs him not to risk his health. George swears that the mailman was mistaken, then relates a strange story from his childhood about a time he beat up a neighbor boy who tried to touch one of his toys. Later, when his mother made him apologize and give the child the toy, George relates that he deliberately dropped and broke the toy rather than letting the other boy have it. This story and his expression of satisfaction that the destroyed toy would always be his frightens Ellen. George then confesses what he wrote in the letter and reveals that the medicine he supposedly spilled the day before, requiring her to re-order the prescription too soon, will seem incriminating. He then threatens to kill her and grabs a gun he has been hiding under the blankets. As she pleads, he suddenly has a heart attack and dies, still grasping the gun. Stunned and afraid when the phone rings and it is the pharmicist inquiring about the prescription, Ellen does not tell him about George's death and is almost incoherent in her explanation. Now fearful that everything she has done will seem incriminating, just as George had predicted, Ellen realizes that she must get the letter back and rushes through the neighborhood, trying to find Carston. Although Carston is initially willing to give her the letter, which she says should not have been mailed, he refuses to relinquish it when he realizes that was from George, rather than her, and tells her that only a supervisor in the downtown office can give it to her. When Ellen returns to the house, George's indulgent aunt, Clara Edwards, is inside, having unlocked the door with a key that she found with a neighbor's help. Ellen is extremely agitated and Clara only agrees to leave without seeing George after Ellen tells her that the visits upset him. Ellen then changes clothes so she can be presentable at the post office and decides to get the gun out of George's hand. It is stiff and she has to pull it out, discharging a bullet. As she is about to leave, Mr. Russell, a public notary, arrives and tries to force his way in to see George, indicating that George had demanded he come that day, no matter what his wife said. Russell does finally leave, but Ellen now fears that he will be another witness against her. At the main post office, the superintendent says he can give her the letter back, but policies about forms and other types of scrutiny that would require George's signature upset Ellen so much that she leaves empty-handed. When she arrives home, Ellen remembers that Ran was supposed to stop by again and calls him not to come. Because he is out making house calls, he does not get the message and arrives almost immediately. She tries to get him to leave by saying that another doctor has been there, but he guesses that George is dead. After Ellen breaks down and tells him everything, Ran finds the gun and the bullet hole in the floor. He then tries to calm her down and tell her that George's mind was going. When the bell rings, she fears that it is the police, but it is only Carston, who returns the letter, admonishing that there was postage due on the thick letter and it could not be delivered. Ellen cries hysterically after Carston leaves and is comforted by Ran, who burns the letter. Calm now, she hopes that someday she can forget what has happened.