Maigret is taken to an inn, the Vieux Garçon, where he finds a loud, drunken fancy dress party in progress. Maigret is pulled into the party by the loudest and liveliest of the young men there; James, and within minutes he’s drinking pernod with him and watching the crowd closely. This is Maigret’s style; he allows himself to blend into the sleazy crowd and is lead across the river to their local. Maigret knows he has found the ‘guinguette a deux sous’ (The Bar on the Seine); a tiny, tawdry bistro, lit by oil lamps, and he knows that somewhere amongst the dancers is a murderer. So he drinks and he watches and he meets all the drunken, laughing people and immerses themselves in their company.

The next day on the river, Maigret meets everyone: Monsieur Basso, a wealthy coal-merchant, rough and ready from working class stock; Monsieur Feinstein, a haberdasher who calls himself Marcel and is always well groomed everyone’s favourite, the loud and friendly James who came alive at night but is bored when sober. They spend their days boating and fishing until they take over the guingette to drink until the early hours of the morning and Maigret joins in, slowly understanding the group and the hints of underlying tensions between them.

Then an afternoon of bridge is broken by a murder. Like a badly acted slow-mo scene from a film, Monsieur Feinstein is shot and M. Basso is found with the gun in his hand, but can’t tell Maigret what happened. The police can’t tell whether Feinstein himself or Basso fired the gun. Maigret senses something is wrong and the case plods along slowly with Maigret depressed by the oppressive late summer heat in Paris and heavy evening thunderstorms. This is a case where the weather and the setting overwhelm the characters in the story. We learn through Maigret that the people themselves and the nature of their loud, raucous parties are the key to solving the crime.