When a jury member takes in the defendant he couldn't convict, she has a bad influence on his son.

Andre Morestan, the blustery, good-natured owner of a Parisian bicycle shop, is called to jury duty and becomes so moved by Natalie Roguin, the pathetic girl accused of murdering her lover, that he holds out for a verdict of not guilty. Once Natalie is acquitted, Andre offers her a job and takes her into his home on the pretext that she is the daughter of an old classmate. Complications arise when Andre's wife Michele becomes suspicious of his story and his son Pierre recognizes Natalie and suspects her of having an affair with his father. Soon, Natalie overcomes Pierre's misgivings, however, and the two fall in love. Trouble comes to the lovers in the form of Robert La Coste, the fiancé of Andre's daughter François, who discovers Natalie's true identity and begins to make advances towards her. To prevent more trouble, Natalie vows to leave the Morestan house and Pierre decides to rob his father's till so that he can run away with her. When Andre discovers the robbery, he accuses Natalie of being guilty all along and orders her from the house. Convinced by Henri Lurette, a fellow juror on the case, Andre goes to the President of the Court to argue for a miscarriage of justice when the judge informs him that new evidence has been found that proves Natalie's innocence. Andre then contritely returns home to welcome Natalie into his family.