The instant New York Times bestseller from the author of the Newbery Medal winner When You Reach Me a story about spies, games, and friendship.

The first day Georges (the S is silent) moves into a new Brooklyn apartment, he sees a sign taped to a door in the basement: SPY CLUB MEETING--TODAY

That's how he meets his twelve-year-old neigh-bor Safer. He and Georges quickly become allies--and fellow spies. Their assignment? Tracking the mysterious Mr. X, who lives in the apartment upstairs. But as Safer's requests become more and more demanding, Georges starts to wonder: how far is too far to go for your only friend?

"Will touch the hearts of kids and adults alike." --NPR

Winner of the Guardian Prize for Children's Fiction
Named a Best Book of the Year by The New York Times, The Wall Street Journal, and more