This was one of a number of times that he and his wife Tigy travelled to various parts of the world. These visits were largely financed by several magazine and newspaper editors who commissioned from him a variety of articles, which they published soon after his return.

Then in the autumn of 1932 he produced the novels Le Coup de Lune (Tropic Moon) with an African setting, L'Âne Rouge (The Night Club), which has echoes of a period in his earlier life in Liège, in Belgium, and Les Fiançailles de Monsieur Hire (Mr. Hire's Engagement).

During part of February and March 1933, he visited various European countries, including Lithuania, Poland, Czechoslovakia, Austria, Hungary, Roumania, Bulgaria and Yugoslavia. Whilst on these visits he kept a record of what he saw through his own photography. This collection of photographs is now kept in the Fonds Simenon (the Simenon Archive) in Liège and from time to time is put on show, as the temporary exhibition in the Galerie Nationale du Jeu de Paume in Paris in early 2004, as well as being reproduced in various publications.

Returning to Marsilly, he reverted to writing L'Écluse N° 1 (The Lock at Charenton) in April 1933, his penultimate Maigret novel to be published by Fayard.

With his focus now on his other novels, he must have wondered what to do with his creation, Maigret. Launched in February 1931 at the spectacular "Bal anthropométrique" in Montparnasse, his Maigret novels had proved a success with the reading public as well as attracting film directors such as Jean Renoir.

In retrospect, it seems logical that Simenon took the obvious step and retired le commissaire Maigret from the French police force, perhaps bearing in mind Conan Doyle's solution for the exit of his creation Sherlock Holmes.

And Simenon was making another move by changing publishers from Fayard (who in the 1920s had published some of his work written under pseudonyms, as well as the later thirty-one volumes under his patronym) to Gallimard. He signed his first contract with Gallimard in October 1933.

For this, his last investigation, Maigret is in the Paris area. And once more it is centred around people who work on the river and in particular at the lock at Charenton (Val-de-Marne), a community that has its own way of life and code. The incident that brings Maigret onto the scene occurs just outside the south-east boundary of the city of Paris, beyond the 12th and 13th arrondissements, at the confluence of the rivers Marne and Seine.

This novel concentrates mainly on the duo of personalities, le commissaire Maigret, who is retiring from the police force in a matter of days, and the domineering Émile (Mimile) Ducrau, a barge and quarry owner. There are other people involved in various ways, mainly family, employees and those of the community, but Ducrau and Maigret's presence dominate the whole investigation. It is almost as if Simenon, as in his other novels, has decided to concentrate on and explore the personality of one person and how events, however small, affect him, with Maigret acting as a kind of mentor.

During those few days in April, there is a rapport that builds up between Maigret and Ducrau, so much so that when the latter learns of Maigret's imminent retirement, he offers le commissaire a lucrative position in his company. Maigret declines the offer, his furnishings have already been moved from his apartment in the Boulevard Richard-Lenoir and he sees his wife off from the Gare d'Orsay so that she can organise their new home at Meung-sur-Loire (Loiret).

At one point Ducrau and Maigret walk along the quayside of the Seine from Charenton to the centre of Paris by way of the Pont de la Tournelle on to the Île Saint-Louis and the Île de la Cité, where they end up at the Tabac Henri-IV, a bar in the centre of the Pont Neuf, which is a meeting place for freighters. En route they learn something of each other's background.

Over the days Maigret moves back and forth along the same stretch of the river meeting up with the same few people, attempting to piece together what he learns and observes with varied success. Later Maigret is invited to Ducrau's house amid the latter's family at Samois-sur-Seine (Seine-et-Marne) near the Forest of Fontainebleau. Here the tension rises as a battle of wills is played out, leaving it to Maigret to defuse the situation and to arrive at the truth.

To date there is only one translation, that by Margaret Ludwig who is one of the few earlier translators to follow Simenon's text faithfully.