Le diamantaire Jeffries a été assassiné dans la somptueuse demeure qu'il occupait à Auteuil. Des brillants ont disparu. Le crime a été commis alors que seuls se trouvaient dans la maison, un vieil ami de la victime, sourd et impotent, la cuisinière et la femme de chambre. La sagacité de l'inspecteur Grey permet de résoudre l'énigme.

A silent film theater projectionist is kidnapped by a gangster group, so he can show them footage of a Dutch jewel dealer they want to steal from. The head gangster's sister helps foil their plan.

Michel Piccoli plays a police inspector whose best friend is murdered on the orders of gang boss Charles Vanel. The inspector knows full well that Vanel is too crafty and well-connected to ever stand trial for his crime, so he carefully lays a subtle trap for his adversary. Unfortunately, both Piccoli and Vanel are thwarted by a pair of scheming females.