Lorenzo Cuni is a fourteen-year-old loner. His wealthy parents think he is away on a school skiing trip, but, in fact, he has stowed himself away in a rarely visited cellar of his parents' house. Surrounded by video games and tinned food, he is perfectly content in his isolation. Then he gets an unexpected visit from his estranged half-sister, Olivia.

Olivia is in her twenties, she's addicted to heroin, and she needs Lorenzo's help. Against his better judgment, Lorenzo lets her stay. Over the next week, they form an intense bond. This brief encounter will change the course of both of their lives.

From the acclaimed author of I'm Not Scared, this is a compulsive exploration of what families keep behind locked doors.