Just before summer begins, 13-year-old Ali finds an odd photograph in the attic. She knows the two children in it are her mother Claire and her aunt Dulcie. But who is the third person, the one who's been torn out of the picture? Ali figures she'll find out while she's vacationing in Maine with Dulcie, in the house where Ali's mother used to spend summers.

But when she meets a girl who keeps talking about someone named Teresa who drowned under mysterious circumstances back when Claire and Dulcie were kids—and whose body was never found—Ali's summer takes a very spooky turn.