Whilst preparing to leave Paris for a forensic training course in Quebec, Commissaire Adamsberg is troubled by an unsolved case from his past. For 30 years he has tried to prove that seemingly unrelated murders are the work of one man, Judge Fulgence, whom he calls The Trident. When a fresh murder takes place he has a hard time convincing anyone of his theory, as the judge has been dead for 16 years. While in Quebec, Adamsberg makes the acquaintance of a young Frenchwoman and when she is found murdered in a similar manner he goes on the run with the hopeless task ahead of him of proving that Fulgence has risen from the grave and recommenced his murderous spree. Ingenious, with oodles of Gallic charm.