From bestselling Spanish author Paul Pen comes a haunting and hopeful tale of discovering light in even the darkest of places. For his whole life, the boy has lived underground, in a basement with his parents, grandmother, sister, and brother. Before he was born, his family was disfigured by a fire. His sister wears a white mask to cover her burns. He spends his hours with his cactus, reading his book on insects, or touching the one ray of sunlight that filters in through a crack in the ceiling. Ever since his sister had a baby, everyone's been acting very strangely. The boy begins to wonder why they never say who the father is, about what happened before his own birth, about why they're shut away. A few days ago, some fireflies arrived in the basement. His grandma said, There's no creature more amazing than one that can make its own light. That light makes the boy want to escape, to know the outside world. Problem is, all the doors are locked. And he doesn't know how to get out...