It could only have happened during the free-love '60s: When Australian-born Jane Alison was 4, her diplomat dad and a friend's father switched places, and families, after falling in love with each other's wives. Amazingly, all four parents seemed to believe things would turn out fine. They didn't. In this wrenching, luminous memoir, Alison explores the incalculable damage done: the fraught, shifting alliances; her guilt as both dads apparently favored her over her doppelgünger stepsister; the crippling shadow her childhood still casts. "Girls who grow up without fathers are so full of longing," a writing teacher tells her. Alison had two, but the longing has never died.