Maigret and the Loner

'People who've been here a long time have been talking about him. This morning, when I was having my coffee and croissants, it was all they were talking about. The old folks, even the middle-aged people, remember him and can't understand how he could have become a tramp. Apparently he was a good-looking man, tall and strong, who had a good profession and made a very decent living. And yet he vanished overnight without saying a word to anyone.'
The death of a homeless man in a condemned building in Les Halles leads Maigret on the trail of the vagrant's mysterious past, and an event that happened years ago in the close-knit community of Montmartre.