Etienne Garnier, manager of an important firm in Cannes, disappears after cashing a cheque for 240 million francs. Inspector Landais and Morel, his colleague, who have been put in charge of the enquiry, find out that the manager had been having an affair. They go off to the missing man's villa and are received by Mrs Garnier, whose personal charm makes a strong impression on the inspector. Certain suspicions attach to the young woman. Morel continues his investigations ; meanwhile relations between Landais and Mrs Garnier become steadily closer. Finally, she gives herself to him and then tells him that she had killed her husband when he, making his escape in a small motorboat, had tried to throw her into the sea. Landais, very much in love, hopes that a plea of legitimate self-defence will save Danièle when she is brought for trial. But Morel, following another line of investigation, has discovered a character whose description corresponds to that of the missing man. Garnier could have escaped from Danièle's attempt to kill him and it must have been he who took for Genoa...