This story begins with the most innocent of domestic scenes. Mary Maloney, a housewife in her sixth month of pregnancy, is waiting for her husband to return home. It is a Thursday night, and they usually eat out. When Patrick Maloney does come home, he is strangely moody and takes a stronger drink than usual. Mary tries to divert him with the usual domestic comforts but to no avail. Patrick asks her to sit down, announcing that he has an important matter to discuss with her. Though the reader is never told, it is clear that Patrick is going to divorce Mary. He ends his speech by saying that he will see that she is provided for and that he hopes that there will be no fuss because it might reflect badly on his position in the police department.
The announcement that she will lose the man around whom her world revolves puts Mary into a daze of unbelief. Instead of arguing with Patrick, she goes on as if nothing has happened, hoping that this will somehow cause her problem to go away. She prepares to make supper and goes down to the deep freezer. She chooses a frozen leg of lamb for the meal. Moving like a somnambulist, she walks into the living room. When Patrick tells her that he does not want dinner, Mary moves behind him and hits him over the head with the leg of lamb.
Patrick falls to the floor with a crash, and this brings Mary to her senses. Mary realizes that she has killed Patrick, and though she is willing to take the legal consequences, she fears for her unborn child, who might die if she is executed. Her mind is now working clearly, and she devises an elaborate deception for the police. She prepares the leg of lamb and puts it in the oven. She then goes to her room and gets ready to go out. As she does so, she rehearses the conversation that she will have with the grocer, trying to get the voice tones and facial expressions as close to normal as possible. This deception is put into operation. She goes to the grocery and uses the exact words that she has rehearsed, so that the whole scene at the grocery appears to be the everyday act of a wife picking up food for her husband’s dinner and chatting with the grocer. She then returns home, telling herself that she must remain natural and to expect nothing out of the ordinary when she enters the house. Thus, when Mary does arrive, she calls out to Patrick as if he were still alive. Her shock at actually finding Patrick’s body is almost completely unfeigned, as if she really did not know that she has already killed him.
Mary then calls the police and reports that Patrick Maloney has been killed. Two police officers, one of whom is Jack Noonan, arrive at the house. Both men are familiar to Mary, who knows most of Patrick’s friends on the police force. They begin the investigation into Patrick’s murder by recording Mrs. Maloney’s story about going out to get food for supper and coming back to find Patrick’s body. Noonan, completely taken in, comforts Mary, asking if she would rather go to her sister’s house or stay with his wife. Mary, however, stays throughout the investigation. When a doctor and other specialists arrive to examine the body, the police conclude that Patrick was killed by a blow to the head with a blunt instrument, probably made of steel.
The police begin searching the house for the murder weapon but with no success. Mary asks Noonan for a drink, then invites him to have one himself. Soon all the police are having a drink, and the investigation has become a consolation scene. Finding that the lamb is now cooked, Mary asks the police officers to eat it because she owes it to Patrick to extend the hospitality of his home to his friends. She finally persuades them to eat the meal as a favor to her. As they do so, they remark that the murder weapon would be very difficult to conceal. One man says to Noonan that the weapon is “probably right under our very noses,” which causes Mary to giggle.