The identity of seventeen-year-old Lucy Stafford's father is a mystery. And she isn't supposed to ask. Her mother has spent Lucy's entire life ducking the topic, while her stepfather answers every question with a hearty, "Have you filled out those college applications yet?" A summer job in a local shop that still develops film fills her time, but when she sees a photo of a man who looks remarkably like her, it also fills her head with ideas. Dusting off Nancy Drew-style detective skills she hasn't used since she was ten years old, Lucy sets out to uncover the mystery of her maybe-father. In the process, she becomes a maybe-stalker with a penchant for ending up in the back of a local police car. Through her misadventures, Lucy uncovers evidence that will force her to confront her mother, her ideas about what defines a father, and the cute French boy with a secret of his own.