Mary Maloney is a homemaker sitting alone and working on her sewing in her quiet, orderly house as she waits for her husband Patrick, a police detective, to come home from work. Mary is six months pregnant. It is Thursday evening, the night of the couple typically goes out to eat, and Mary has the set-up for pre-dinner cocktails already prepared.

When her husband arrives, Mary greets him warmly. But her repeated offers of affectionate attention are all rebuked by clipped and dispassionate responses from Patrick. She prepares a weak cocktail for herself and a stronger one for Patrick who, uncharacteristically, downs the drink quickly, then pours and consumes a more potent second drink. Quietly alarmed, Mary suggests that Patrick eat some crackers and cheese, which he refuses. Mary then offers to forego their date night and prepare a home-cooked supper, suggesting, perhaps, some lamb chops or pork from the freezer downstairs. Patrick ignores the offer and orders Mary to sit down; he has something to tell her. At this point, her alarm turns to fear.

Patrick attempts to prepare Mary for some shocking news, claiming he has thought about it a lot and that he thinks it best to simply blurt it all out. Though his confession is not specified in the narrative, it becomes clear that Patrick intends to leave Mary. Patrick admits he knows his confession comes at a bad time, presumably, though he doesn’t say so directly, because Mary is pregnant. He tells her he will continue to provide her with financial support, and that he hopes everything will be handled discreetly because otherwise it would be bad for his job.

At first, Mary is stunned and uncertain. She decides that if she behaves as if nothing has happened, she can perhaps undo the damage. Without any direct verbal response to what he has said, she tells Patrick that she is going downstairs to get the meat for dinner, and he does not deter her. Hollowed and stupefied, Mary descends the steps to the cellar, retrieves a leg of lamb from the freezer, and carries it upstairs to prepare a meal. She sees Patrick standing near the window with his back to her. Without turning around, Patrick tells Mary that it is ludicrous to make dinner for him because he is going out.

Upon hearing these words, Mary walks up behind Patrick and brings the frozen leg of lamb down on his head in one unmitigated blow. His body undulates as if in slow motion, then drops dead to the floor, overturning a small table.

In the minutes after the killing, Mary gradually returns to full lucidity. She contemplates with neither concern nor regret, only resignation, that she may be executed for what she has done. It occurs to her to wonder what may happen to the unborn child of a pregnant murderer, and she immediately resolves to be proactive about her situation. She carries the meat into the kitchen, turns on the oven, and places the leg of lamb inside. Mary then practices her smile and tone of voice. It becomes clear that she is rehearsing to purchase potatoes and peas from a grocer named Sam.

Mary hurries out onto the street and goes to the grocery store where she addresses Sam, using the exact dialogue she rehearsed earlier. Sam is clearly familiar with Mr. and Mrs. Maloney, so Mary refers to her husband by his first name and tells Sam that Patrick has decided he is too tired to go out to eat tonight. Sam is attentive, and the two confirm that Mary has already started cooking a frozen leg of lamb.

As she returns home, Mary mentally prepares herself for the cover-up she must create in order to deflect suspicion and make Patrick’s death appear to be the result of an encounter with an unknown murderer. She goes so far as to call out to Patrick as if he could answer her, and the “discovery” of his body causes Mary to experience real, cathartic emotion that plays naturally into her overall charade.

Mary then proceeds to phone the police station where Patrick works, reporting in a heightened state of urgency that she thinks her husband is dead. The police officers who quickly arrive at her house are Sergeant Jack Noonan, whom Mary knows well, and another named O’Malley. Noonan is kind and chivalrous to Mary, as are all the investigators who show up including a doctor, two detectives, a police photographer, a fingerprint expert, and a few others. They sweep through and around the house, asking Mary questions and inspecting the crime scene. Two attendants arrive and remove the corpse. As the minutes pass, Mary picks up on every subtlety of the procedures. She takes in snatches of hushed conversation regarding the investigation, including notations from a brief interview with Sam, the grocer.

Eventually, Noonan suggests Mary find a place to stay and offers to let Mary stay in his own home with him and his wife. Mary rejects the offer, saying that she is too emotionally spent to move from her chair. The number of investigators begins to dwindle, but the process continues around her as Noonan explains that the focus is now on finding the murder weapon. The police believe it must be a large, heavy metal object that is likely still somewhere on the premises.

Mary suggests that a few sips of whiskey might have restorative powers for her. As Noonan accommodates her request, she proposes that perhaps he and the few remaining investigators might also be restored by a small drink. Hesitantly, each of the men accepts. Noonan points out that the leg of lamb is still cooking and offers to turn off the oven. Grateful, Mary expresses to Noonan that the investigative team must be hungry by now, and that the departed Patrick would want her to be hospitable to his colleagues. They would be doing her a great favor if they would dine on the now fully cooked lamb, which she can no longer bring herself to eat.

Though reluctant to accept at first, the team is genuinely hungry and they ultimately acquiesce. While seated around the kitchen table, they engage in a hearty discussion about how the doctor’s report on the deathblow indicates that the murder weapon must have been heavy, too awkward to be easily removed, and is probably somewhere nearby. Oblivious, they eat the leg of lamb while they talk, unaware that the murder weapon is indeed right under their noses.

Mary, still seated in the living room, listens and giggles quietly to herself.