In 1977, on the Promenade des Anglais, a war is raging between two casinos: the venerable Palais de la Méditerranée, which brought prosperity to the Riviera and which Renée Le Roux inherited upon her husband's death, and the Ruhl, a flashy new establishment run by a shady clan, linked to the Italian Mafia and the mayor of Nice, Jacques Médecin, seeking to secure a local monopoly on gambling. A lawyer with a troubled personality, Maurice Agnelet convinces his mistress Agnès, 29, the third of the four Le Roux children, to sell her shares to the owners of the Ruhl for 3 million francs, thus sealing her mother's defeat. Four months later, on October 27, the young woman disappears without a trace. Her body will never be found.

Convicted of financial embezzlement, Agnelet, struck off the bar, served two years in prison in France. Upon his release, he was caught up in the stubbornness of Renée Le Roux, who devoted what remained of her fortune to tirelessly searching for the fate of her daughter.

In March 2014, thirty-seven years after the disappearance of Agnès Le Roux, a diminished old man appeared, free, at the Rennes Assizes, supported by his youngest son, Thomas. Maurice Agnelet, 76, persists in claiming his innocence.