It's the summer of 1940 in German-occupied Paris, and Detective Henri Lefort has been given five days to solve the murder of a German major that took place in the Louvre Museum - or his own neck will be on the line. Blocked from the crime scene but given a list of suspects, Henri encounters a group of artists, including Pablo Picasso, who know more than they're willing to tell him. With the help of a police secretary, he must unravel their connections to the murdered officer and to each other.

While hunting the killer, Henri must also keep the secret of his own past under wraps as someone threatens to expose him. But when he meets a famed psychoanalyst who promises to help him, he begins to tell his story of his time in World War I - but his biggest secret, if revealed to the wrong people, will not just end his career, but almost certainly see him hanged for a decades-old murder he didn't commit.

Over the course of the next five days, with the clock ticking to name a murderer, Henri's loyalty to his country and to his fellow Parisians is tested under the pressure of the German officers.