An FBI agent with a background in cryptography. A brilliant game maker bent on revenge. A deadly battle of wits and wills. An ingenious thriller from the Wall Street Journal bestselling author of The Cipher.

FBI agent and former military codebreaker Daniela "Dani" Vega witnesses a murder on a Manhattan sidewalk. The victim is chief of staff for a powerful New York senator. The assassin turned informant is Gustavo Toro. His code: hit the target and don't ask questions. When Dani suspects a complex conspiracy, the only way to take down the mastermind is from the inside, forcing her to partner with Toro. Together they must infiltrate the inner circle at a remote facility.

Except it's a trap. For all of them.

Locked in a subterranean labyrinth and held captive by an unseen host, Dani, Toro, and others must fight for their lives. Now Dani must stay undercover, unravel a bizarre conspiracy, and survive lethal puzzles. But will Toro be friend or foe? Because in this killer's game, everything is real: the paranoia, the desperation, and the body count. And only one person can make it out alive.