Hoping to make a career in gangsterism, Jojo, a young rascal, demonstrates his know-how by stabbing a passer-by in broad daylight. However, the victim was making a film, and the crime was recorded. In charge of the investigation, Superintendent Bernard, a fine sleuth who takes himself for Maigret, has the sequence projected and extracts a portrait of the murderer. One of his men thinks he recognizes a clown from the Médrano circus, who is immediately arrested. But the latter has a twin brother as a partner: each accuses himself to exonerate the other. Two suspects are better than one, we keep them both behind bars at the Sûreté. However, the real murderer is still running: he is a double of the antipodist twins. It takes the intervention of Titine - a lady of light morals, but with infallible memory, who spent the night with this third thief - for the light to shine. Only a woman, preferably venal, was able to disentangle the truth from the false, the reality of its simulacra. In bed, a man discovers himself, without possible illusion - Jojo, confused, will be shot at the very scene of his crime, by the leader of the gang in which he wished to be admitted. What despair of being dishonest. This settling of scores will also be disguised as suicide, to the chagrin of the police commissioner, who will see nothing but fire.