Mary’s go-to illness is to claim that her heart hurts or that she feels a pain in her heart. Practically and literally, this is a well-practiced ploy that consistently receives results. As Mrs. Mortar points out, “Heart trouble is very serious in a child” (13), and it undoubtedly buys Mary the time it takes to call a doctor. Metaphorically, Mary’s ailing heart represents the sickness in her developing personhood, identity, and morality. She spreads this metaphorical sickness by influencing other children to misbehave. Mary’s bad heart is as essentialized as Martha’s supposed lesbianism. As Karen tells Mrs. Tilford, “Your Mary’s a strange girl, a bad girl. There’s something very awful the matter with her” (51). When Mrs. Tilford finally discovers that her granddaughter has lied, she describes Mary’s continued presence in her home as a punishment she is exacting upon herself. There is no suggestion that Mary, who is only 14, might be able to learn new behavior.

In Act I, when Mary and her friends are alone in the school’s living room, Mary accidentally knocks a vase on the floor. As it breaks, “Evelyn and Peggy gasp, and Mary’s bravado disappears for a moment” (24).