Newly married lawyer Lucien Lambert allows his brother to persuade him to take on a case that could make his name as a top notch defense lawyer. This is how Lucien meets the client Blanche Kaplan, who is suspected of her husband’s cold-blooded murder. Although Blanche has a perfect alibi, the murder weapon – the knife with which Paul Kaplan was stabbed to death – is covered with her fingerprints. During his research Lucien begins to investigate the Kaplan’s empty house in detail. Here he meets the beautiful yet mysterious Marguerite, who has taken over the house, as if it belonged to her. Lucien and Marguerite embark upon a game that is a mixture of persecution and seduction. Before long, they begin to behave like a married couple: he comes home from work, she makes their evening meal, they eat and talk about life and love. These goings-on are observed by Louis Berger, a plain-clothes policeman. During one of their nightly encounters, Marguerite admits to Lucien that she had an affair with Paul Kaplan, which also makes her a suspect. Now for Lucien it’s too late for such considerations. Not only does he understand Marguerite – he has fallen head over heels in love with her. But Lucien is a married man and, additionally, somewhere out there Louis Berger is still searching for the truth.