Thirteen-year-old first-person narrator Ali, looking for something to read, opens a box of books her mother brought from her deceased grandmother’s house. Picking at random, she opens The Bungalow Mystery by Carolyn Keene, and out falls a torn photograph of her mother, Claire, and her aunt Dulcie posing near a lake. Ali estimates that they were around nine or 10 and 11 respectively at the time it was taken. Next to Dulcie, Ali guesses, is a girl but only “an arm, a shoulder, and a few strands of long hair” are visible (2); the rest of the image has been torn off. A note at the back reads “Gull Cottage, 1977. Dulcie, Claire, and T—” (2).

Ali shows her mother the photo, and, seeming flustered, Claire asks Ali where she got it. Her reaction surprises Ali. Muttering to herself, Claire swears she threw the picture away. Ali asks about the girl in the photo, but her mother pretends not to notice the arm or hair, saying she does not remember anyone other than her sister ever being at the lake. Ali’s father, Pete, returns home, notices the arm in the photo, and begins to ask the same questions as Ali.