Part 1 - The Camp (Past): Young Adam Tattleman, who suffers from asthma, attends a summer pen-and-paper RPG camp. There's a mysterious Russian exchange student counselor who calls himself "Ubitza Krollikov." This counselor has unusual survival skills - he hunts, traps, kills and eats rabbits around the camp. He's rough around the edges and gives campers sleeper holds that make them pass out, which the kids treat like a thrill-seeking experience.
When a camper is found murdered via sleeper hold, all suspicion falls on the Russian counselor. He disappears before he can be questioned. When the camp tries to follow up with the Russian exchange program, they discover they never actually sent anyone - the counselor was a complete fake.
The campers eventually figure out that "Ubitza Krollikov" literally translates to "Killer of Rabbits" - he had been telling them what he was all along.
Part 2 - The Neighborhood (Present): Years later, Adam has grown up and overcome his childhood asthma. He moves to a new neighborhood where, by chance, he spots the fake Russian counselor - now going by another identity and working some kind of small local job.
When Adam recognizes him, knowing he's a murderer who was never caught, the shock triggers his asthma to return. Now Adam must decide what to do, knowing a killer is living in his neighborhood under a false identity.
What ensues is a game of cat and mouse as the two, who recognize each other, attempt to achieve their mutual aims- Ubitza to maintain a low profile despite his mysterious past, and Adam, to live as an adult despite his childhood boogeyman moving into the neighborhood.