Agent Seventeen, the most infamous hit man in the world, has quit. But whoever wants to become Assassin Eighteen must track him down and kill him first. So when a bullet hits the glass inches from his face, he knows who fired it. Doesn't he? It turns out that the sniper isn't the hardened killer he was expecting. It's Mireille, a mysterious silent child abandoned in the woods with instructions to pull the trigger. Reuniting with his spiky lover, Kat, Seventeen has to protect Mireille and discover who sent her to kill him and why. But the road he must travel is littered with bodies. And the answer, when it comes, will blow apart everything Seventeen thought he knew.

Behind the events you know are the killers you don’t. When diplomacy fails, we're the ones who gear up. Officially we don’t exist, but every government in the world uses our services. We’ve been saving the world for 100 years. Sixteen people have done this job before me. I am Seventeen. The most feared assassin in the world. But to be the best, you must beat the best. My next target is Sixteen, just as one day Eighteen will hunt me down. It’s a dog-eat-dog world, and it gets lonely at the top. Nobody gets to stay for long. But while we're here, all that matters is that we win.