Caroline and François come from a dynasty of cops. Although they're siblings, they form an unorthodox pair of detectives, with methods that complement each other quite well even though sometimes conflicting. She is on the "hyper" side, thinking and acting like a typical member of the anti-crime squad of Paris' notorious Seine-Saint-Denis suburb; he is the tortoise of the fable, moving slowly but steadily, using his knowledge of animals to decipher people's behavior. This "town and country mouse" tag team appears ruthless, tight, unshakable but as they go about their investigations, they can't help replaying their sibling quarrels, which reflect their respective emotional wounds, yet to be fully healed.