Maigret is investigating the famous impostor Pierre, called 'The Latvian', who is currently in the company of millionaire Strophades. The Commissioner knows that Pierre is going to betray the millionaire, but Strophades ignores all warnings. While Maigret waits for further developments, a dead man is found in an express train, who looks very much like Pierre. The Parisian investigator has to pay for the clarification of this crime with the loss of one of his dearest colleagues... Based on the 1st Maigret novel Pietr le Letton (1929), published in German as Maigret und die Zwillinge and later as Maigret und Pietr der Lette.