Three years ago, Saga Bauer received a postcard with a threatening text about a gun with nine white bullets - one of which is waiting for Detective Joona Linna. But time passed and the threat faded. Until now. A sack with a decomposed body is found tied to a tree in the forest. A milky white bullet casing is found at the murder scene. And soon the police are sent complicated riddles from the killer - a chance to stop further murders. Joona Linna and Saga Bauer must fight side by side to solve the puzzle and save each victim before it's too late. But the violent hunt becomes increasingly desperate. Maybe this serial killer is unstoppable. Maybe they're already caught in the web . . .