A young man brings Inspector Torrence a message he found in a bottle drifting on the Seine. It is a desperate call; an old man is sequestered in an abandoned mill that water is gradually invading ... The O Agency is investigating ...

In order to be able to touch the heritage of Chauffier-Mignot; Jean Dassonville wants to marry Cécile the daughter of the family. The father not agreeing, he decides to kidnap him and lock him up in an old water mill. But Chauffier-Mignot refuses to sign the marriage authorization and even succeeds in sending a message in a bottle thrown into the river ...

The banker's mistress was murdered in broad daylight, in the open sea, in full sun, in the sight of three witnesses. Fortunately, Émile, from the O Agency, knows the secrets of the bowling alley and the technique of boulantin fishing with piades. Without these talents of society, the mystery would have remained intact, and the murderer unpunished.