Maigret and the loner

It was August and over half of his inspectors, along with most of Paris, are on holiday. Things are fairly quiet. Then Chief Superintendent Maigret receives a telephone call about the murder of an unidentified vagrant near Les Halles, the old central market. The man was found laying on a bed, fully dressed, in an upper room in a long-condemned building. His clothes were those of a tramp, but he had neatly trimmed hair, and mustache with goatee. In addition, his hands were carefully manicured. The few people in the district who recognize his picture admit they don’t actually know him – no one knows his Christian name. So, why did someone track him down in his lair, and who?