Working on an archaeological dig to uncover an ancient Viking fortification on the Swedish island of Gotland, a group of students becomes caught up in a web of horror when a young woman turns up dead, naked, and hanging from a tree, the victim of a ritual killing.

Karin Jacobsson, Anders Knutas's newly promoted deputy, starts a complex inquiry into a murder committed while Knutas is on holiday. Peter Bovide, the owner of a small construction company, has been camping on the island of Faro with his wife and children. One morning, Bovide fails to return from his regular morning jog, and his bullet-ridden body, including multiple stomach shots after one to the head, turns up shortly afterward.