A body is discovered under an avalanche in the Westfjords of Iceland, and detective Hildur Rúnarsdóttir begins investigating an extraordinary murder. Hildur's investigative team is joined by Finnish police trainee Jakob Johanson and German trainee Florian Herrmann.

A second murder takes the investigation to Reykjavík, and the signatures left by the perpetrator link the cases together. Pressure mounts both in the investigation and in the personal lives of Hildur and Jakob.