Louis Kelveler, nicknamed the German, a born detective expelled from the Ministry of the Interior for knowing too much, finds a suspicious bone under a tree. With this discovery - a phalanx of a human finger that ended up in Paris in the stomach of a vicious pit bull - an investigation begins that leads Kelveler to a remote corner of Brittany. An unusual trail will help Louis, driven by an indomitable thirst for justice, with the help of two young historians - Mark Vandusler and his friend Mathias - to find a brutal killer who is confident in his invulnerability.