The instant New York Times bestseller from the author of the Newbery Medal book "When You Reach Me" a story about spies, games, and friendship. Seventh grader Georges moves into a Brooklyn apartment building and meets Safer, a twelve-year-old self-appointed spy. Georges becomes Safer's first spy recruit. His assignment? Tracking the mysterious Mr. X, who lives in the apartment upstairs. But as Safer becomes more demanding, Georges starts to wonder: what is a lie, and what is a game? How far is too far to go for your only friend?