Nice, 1970s. Renée Le Roux runs Le Palais de la Méditerranée, the jewel of French casinos, with an iron fist. But the establishment is taking on water, ruined by poor management and assailed by competition.

Renée Le Roux is now the new manager of the Palais. But when she refused to appoint him general manager, Maurice Agnelet promised revenge. He then seduces his daughter Agnès, whom he knows is madly in love with him.

Agnès has disappeared. It has now been four months since anyone has seen her. Alerted by Renée Le Roux, the police discover a mysterious farewell note in Agnès' apartment that suggests that she has committed suicide. But Renée Le Roux refuses to believe it.

The years go by and the case gets bogged down. Only Renée Le Roux continues the fight to discover the truth about Agnès' death. Convicted on the financial aspect of the case, Maurice Agnelet was imprisoned.