According to a different source, this question refers to the story "Lamb to the Slaughter" by Roald Dahl.
In this story, Mary is a devoted wife who nevertheless kills her husband when she finds out that he wants a divorce. After killing him, Mary coldly and carefully plans a way in which she will not be accused of the crime. This influences the outcome of the story, ensuring that Mary is not blamed for the murder.
For example, Mary goes out after the murder and talks to the grocer for a while. This allows Mary to have an alibi in case she is considered a suspect. Another example is the way in which Mary cooks the lamb leg that she used to kill her husband. This allows her to hide the weapon, as well as to further develop her image as a perfect wife.
