Bobby (Robert Verdier) is a professional swindler who is well known by the police: some months ago the inspector Doirel has tried to catch him, because every time Bobby has managed to have excellent alibis.While he was doing a burglary,he becomes witness of a murder and goes away, because he is afraid of being accused for the murder, but he will be arrested by the inspector Doirel.With the help of Monique, a bar hostess and friend of Bobby the inspector Doirel must prove the innocence of Bobbby and catch the real murderer.