New York Times bestselling author David Levithan takes young readers on twisting journey through truth, reality, and fantasy and belief. Aidan disappeared for six days. And just as suddenly as he vanished, Aidan reappears. Where has he been? The story he tells is simply. . . impossible. But it's the story Aidan is sticking to. His brother, Lucas, wants to believe him. But Lucas is aware of what other people, including their parents, are saying: that Aidan is making it all up to disguise the fact that he ran away. The kids in school taunt him, but still Aidan clings to his story as Lucas becomes more concerned. Being on Aidan's side would mean believing in the impossible. But how can you believe in the impossible when everything and everybody is telling you not to?