Three years ago, Detective Saga Bauer received an ominous postcard describing a gun and nine white bullets - one of which was intended for her partner, Detective Joona Linna. The sender alleged that Saga was the only person who could save him. But as time passed, the threat faded.

Until now.

A sack with a decomposing body has been found hanging from a tree in the forest. A milky white bullet casing turns up at the scene. When the body count begins to rise, the police realise that the killer is sending riddles, offering them the chance to stop the murders before they happen.

But the police always seem to arrive a moment too late. As they begin to close in, the case becomes more and more tangled. Someone is spinning a fiendishly intricate web, pulling Joona ever closer to a trap he may not be able to escape.