Фред Варгас — библиография

A woman is found dead in her bath. The murder has been disguised as a suicide and a strange symbol is discovered at the scene.
Then the symbol is observed near a second victim, who ten years earlier had also taken part in a doomed expedition to Iceland.
How are these deaths, and rumours of an Icelandic demon, linked to a secretive local society? And what does the mysterious sign mean? Commissaire Adamsberg is about to find out.