A man mysteriously vanishes on his way to work in Fjällbacka. His wife and children have no idea where he could have gone. Four months later, Patrik Hedstrom at the Tanumshede police force gets a call: the man has been found murdered, frozen underneath the ice.
The case takes a sudden turn when it emerges one of the dead man's friends, author Christian Thydell, has been receiving anonymous death threats. Christian is on the brink of making it big with his breakthrough novel The Mermaid. When he receives another ominous message during the launch party, Christian breaks down and shows the letters to Erica, who is pregnant with twins.
She has long suspected that something is tormenting Christian and ignores his pleas to leave the police out of it. Erica sneaks one letter away to show Patrik, who instantly realizes the danger Christian is in. This is someone carrying a deep hatred for Christian, someone confused and unstable who wouldn't hesitate in turning the threats into reality.
And when yet another man is found murdered, the police realize there is a connection between the killings, which leads them into the dead men's pasts...