The acclaimed, New York Times bestselling author of The Book of Ruth and A Map of the World returns with a stunning coming-of-age novel about girls, mothers, and finding one's way in the world.

Seventeen-year-old Phoebe was never interested in her birth family. But on the cusp of her high school graduation, her adoptive mother, Greta, insists on a visit to meet her biological parents and siblings. The encounter is a jolt, a revelation that derails Phoebe.

With the help of her best friend Luna, Phoebe runs away—as far as their friend Patrick O'Connor's chaotic home, where she hopes to go unnoticed among his thirteen siblings. But when Phoebe asks Patrick to chop off her hip-length hair, she's suddenly transformed. Patrick's older brothers can't help but notice the striking, Peter Pan–like stranger who has suddenly appeared in their midst.

What starts as an adolescent rebellion soon spirals into a whirlwind of self-discovery and unexpected connections. As she grapples with her shifting identity and strained relationships, Phoebe must navigate the tumultuous road out of girlhood and chart a new and unknown course.