Keeping watch under the windows of the Paris flat belonging to a politician's nephew, ex-special investigator Louis Kehlweiler catches sight of something odd on the pavement. A tiny piece of bone. Human bone, in fact. When Kehlweiler takes his find to the nearest police station, he faces ridicule. Obsessed by the fragment, he follows the trail to the tiny Breton fishing village of Port-Nicolas - in search of a dog. But when he recruits 'evangelists' Marc and Mathias to help, they find themselves facing even bigger game.