In "Lamb to the Slaughter," Dahl uses indirect characterization to describe the personality traits of Mary, the story's main character. In the opening line, for instance, we see Mary is an organized person through her attention to detail in preparing the house for her husband's arrival:

The room was warm, the curtains were closed, the two tables lamps were lit.

This also demonstrates another of Mary's personality traits: she likes routine. When her husband goes to fetch a drink for himself, for instance, Mary moves "uneasily." This shows she does not like changes to her domestic routine.

Mary is also very domesticated: she tends to the home by cooking and cleaning while her husband is at work. That she cares for her husband's every whim also shows how loving Mary is. This is further reinforced by her denial when he tells her he wants a divorce:

Her first instinct was not to believe any of it. She thought perhaps she'd imagined the whole thing.

Mary has a darker side, though, one which is characterized by the deception she displays after murdering her husband. She claims to the police, for example, that she has no idea how her husband met his death and, in an ironic twist, lets them eat the leg of lamb she used in the murder.