On the outskirts of Paris, two men have been found with their throats cut, and despite the common assumption that the crime is a drug-related incident, Commissaire Adamsberg becomes convinced that the deaths are the work of a serial killer with split personalities and enlists the assistance of pathologist Ariane Lagarde to help him unravel the truth.

"A woman is found murdered in her bathtub, and the murder has been made to look like a suicide. But a strange symbol found at the crime scene leads the local police to call Commissaire Adamsberg and his team. When the symbol is found near the body of a second disguised suicide, a pattern begins to emerge: both victims were part of a disastrous expedition to Iceland over ten years ago where a group of tourists found themselves trapped on a deserted...