A First Class Murder

Maigret is called for by his nephew, a new inspector in the north after a man was found dead in a first class carriage. The 106 train to Paris which started outside France was stopped at the Jeumont station for 50 minutes during which the murder took place. His nephew had the carriage and dining car detached and isolated but ran foul of politics as a French Consol and his family, secretary, and nanny were on board. The victim's identity papers were stolen and the train is filled with a mixture of the guilty and the innocent and dentists. But of the murder? And who is and what happened to Max?