A leak occurred at the O Agency. What should at all costs remain secret fell on the ears of thugs who took advantage of it to exercise blackmail, and also to make the police believe that the Agency itself, even is wet in the combination. Dispelling police suspicion is far from easy. Until a few acoustic properties are discovered.

The painter Tigrane Alban murdered Evjen because he had dishonored his daughter Dalté. The members of the O Agency are the only ones to know about it, but soon the painter is blackmailed. So there is one of the members of the O Agency who is responsible for the leaks. Miss Berthe feels that everything accuses her ...