The theme of identity is treated in the setting of "Lamb to the Slaughter" by showing the manner in which Mary Malone's housekeeping denotes a high degree of comfort, submissiveness, and joy. The setting elicits these emotions from Mary, but will later on contrast dramatically with the events that are going to take place.
The room was warm and clean, the curtains drawn, the two table lamps alight-hers and the one by the empty chair opposite. On the sideboard behind her, two tall glasses, soda water, whiskey. Fresh ice cubes in the Thermos bucket.
The manner in which Roald Dahl presents this scenario is indicative of a life where routine is more than welcome because it is enjoyable, at least to Mary Malone. The scene depicts basically who she is: someone willing to please her husband, willing to "wait" on him, and more than willing to abide by his rule as the man of the house. When Patrick breaks the news to Mary that he will leave her, her identity as wife and future mother crashes for good, making her snap. It is precisely the fact that her identity was so solidly grounded in her psyche that made her lose herself to the sudden shock of seeing it all go away.