"Lamb to the Slaughter" is one of my favorite short stories by Roald Dahl. Basically, it is about Mary Maloney, a pregnant housewife, who kills her husband after he tells her he's leaving her. Mary's life revolves around her husband, Patrick, and she's in shock after his news. She kills him with a frozen leg of lamb, and after her panic subsides, she comes up with an ingenious way to prevent the police, her husband's friends, of ever suspecting her of the crime. She puts the lamb, the murder weapon, in the oven, goes to the market to establish an alibi, goes back home, and calls the police. The policemen who respond to the scene treat her kindly, and she ends up feeding them the leg of lamb. Mary smiles as they eat the evidence and discuss finding the murder weapon, knowing it's probably "right under our very noses".
I have provided a link to the full summary of the story provided at enotes.