Six-months-pregnant Mary Maloney sits in her home with the curtains drawn as she waits for her husband, Patrick, to come home from work. She calmly looks at the clock, and at 10 minutes to 5, his car pulls into the driveway and she leans in to kiss him as he comes to the door. She hangs his coat, and makes them drinks. This is a blissful time of day for Mary, and she waits quietly by her husband while he finishes his drink. Mary really loves her husband and enjoys basking in his warmth "as a sunbather feels the sun" (404).
Mary asks her husband if he is tired, and he downs his whiskey soda, which is very unusual for him. Her husband stands up to get another drink, but Mary jumps up and asks to bring it to him. Her husband tells her to sit down, and when he returns she notices the drink is filled with significantly more whiskey. Mary comments on how her husband should not be on his feet all day given how senior of a policeman he is, and her husband does not respond. Mary's husband continues to sit in silence as she tells him she can make him dinner, even though they usually go out to eat on Thursdays. He does not respond, so Mary insists that her husband must eat something until he tells her to sit down.
When her husband sits her down, Mary sees him sitting motionlessly, shrouded by a shadow, as he tells her that he is going to leave her. Mary watches him with a "dazed horror" (405), and her husband tells Mary not to make a fuss about the divorce, as it would be bad for his job.
After hearing this, Mary walks down the stairs to the cellar and lifts the first object she grabs, a leg of lamb, from the freezer. She decides to make lamb for dinner as she holds the lamb by the thin bone-end. Since he is going out, her husband tells her not to bother making dinner. In response, Mary walks up behind him, swings the leg of lamb, and brings it down onto the back of his head.
Her husband remains standing for four or five seconds, then falls to the carpet, dead. She snaps out of shock and thinks clearly about her next steps. Mary initially decides the penalty for killing her husband would be a relief. But, she worries about her unborn child, and whether they would kill both her and her child or wait until the child was born.
Mary carries the meat into the oven and begins to cook it. She then begins to tidy up her face and smile strangely at the mirror. After rehearsing in the mirror, Mary smiles and speaks more naturally, and she goes to the grocery store to buy some potatoes and peas. At the grocery store, Mary lies to the cashier that she and her husband decided to eat in.
Returning from the grocery store with potatoes, peas and cheesecake, Mary decides to make supper as she usually would, and to make it as tasty as possible. Mary's plot is to tell the police her husband is murdered while she is buying vegetables, and she finds his body when she returns home. Mary plans to keep her actions as natural as possible, and even calls to her husband as she walks through the door with the groceries. As she is acting out her plan, she truly feels the shock of his death, and she begins crying over his dead body. Mary then calls the police to report her husband's murder, and the police car arrives at her home.
Two policemen from the precinct walk into her home, and she knows both of them. She falls into one of the policemen's arms, weeping hysterically, and he gently puts her in a chair. Mary tells the policemen about her visit to the grocer, and after one of the policemen finds a small patch of blood on Patrick's head, more men come into her home. A doctor and two detectives examine the body and the crime scene.
Eventually, the photographer and doctor leave, and two other men carry Patrick's body out on a stretcher. Mary asks to stay in the house while the two policemen search her home, and they tell her that her husband was killed by a heavy blunt object, most likely a large piece of metal. The policemen continue to search her home for the murder weapon, and Mary offers them whiskey.
One of the police officers remarks that Mary still has lamb in the oven, and Mary persuades the policemen to have the lamb for dinner. The story ends with the policemen discussing the murder weapon that it is likely "right under" their noses, as they eat the leg of lamb.
In "Lamb to the Slaughter," the tranquility of Mary's home life as a doting wife and soon-to-be mother is destroyed by her husband's wish to divorce her. The beginning of this story sets up her complete servility. Indeed, she is given no interests or thoughts outside of caring for her husband and waiting for him to arrive, as she notices every move her husband makes. When her husband unsettles their marriage by asking for a divorce, he also unsettles Mary's stability, shattering her internal life and beginning her transformation into a murderer.
As Mary's husband tells her that he is going to leave her, Mary acutely observes several changes in his usual demeanor. Like a predator, Mary observes that he downs his drink too quickly. Mary does not see this, but hears it, as the ice clinks in his glass. She then notices "the light from the lamp beside him [falling] across the upper part of his face, leaving the chin and mouth in the shadow" (405). This light casts her husband ominously, as the darkness around his mouth foreshadows his impending dark confession as he unravels the stability of their marriage.
Indeed, Mary changes instantaneously, as her movements become "automatic" (406) while she walks down to the freezer, picks out the leg of lamb, and kills her husband with it. Murdering her husband only requires one precise blow, and Mary's transformation from docile wife to calculating murderer is immediate. Mary's previous daze is replaced by a feeling of "cold and surprise," and a mental clarity that allows her to think quickly. The shift into cold and surprise symbolizes Mary's rebirth as a calculating killer, as Mary devises a plot to clear herself of any suspicion.
After the beginning of the story establishes Mary as someone whose only thought is to care for her husband, her inability to access emotion naturally after her murder, to the extent that she must practice her expressions in the mirror, shows her external and internal transformation. Her husband's ill-treatment of her, and the revenge that she exacts, change her immensely. As Mary returns to her home and calls the police, she reassures herself that she does not have to act. But this repetitive thought casts doubt on Mary's credibility: can she really still lament her husband's death after murdering him? Mary tells herself to "do everything right and natural" (408) so she will not need to act, as she pretends to be the faithful wife that she was before the murder.
Mary's final murderous act, her decision to feed the detectives the leg of lamb that she used to kill her husband, shows the extent of Mary's depravity. But, this act also displays a reaffirmation of power. After devoting herself to her husband patiently, she is dumped by him while she is six months pregnant. Her servility to her husband is upturned when she kills him with the dinner she planned to make him, as she vengefully murders her husband after he metaphorically kills their marriage. This act, though insidious, allows her to break from her obedience. When she feeds the police officers the murder weapon, she again unsettles the expectation that she will be a good wife. Indeed, her act of hospitality, an expectation from a good housewife, is instead an act of exoneration, as she removes the evidence and any chance that she will be convicted. Mary feeds her rebellion and revenge directly to the detectives, as they unknowingly consume Mary's disruption of her expected domestic and gender roles.