The story begins with Paris on the threshold of spring. It is March, Madame Maigret is away in Alsace to be with her sister who is soon to give birth to her third child, and Maigret finds himself without any urgent cases to mull over. This is unusual for him, because Maigret has a passion for his job which tends to keep him busy almost without letup. On this particular day, he receives in the mail a letter from a former colleague, Leduc, who had retired from the Police Judiciare 2 years previously to live a quiet, contented life in the Dordogne. Leduc tells Maigret: "... if ever a good wind should blow you into this part of the world, I count on you to spend a few days under my roof. My old servant is never so happy as when there's a guest to be made a fuss of... The salmon fishing has begun..." So, as Maigret has no impending case or cases at the moment, he resolves to travel by train to see his old friend in the Dordogne for a few days.
Maigret shares a berth on the train with a rather strange, nervous, fidgety man who closets himself in the upper bunk of the partition. He sleeps fitfully. So on edge is this man that Maigret is denied a good night's rest. Then suddenly, with Maigret laying uncomfortably in bed, he notices the man's lower legs hang over the upper bunk railing as he puts on a pair of woolen socks and leather boots, clambers out of his bunk, walks quickly down the adjoining passage, and jumps off the train. Maigret follows close behind him, wondering at the strangeness of the situation, the train now moving slow enough for him to jump to the ground without injuring himself when there is a sudden flash and a bullet pierces his shoulder. Vainly, Maigret is in pursuit of the man and slips into unconsciousness from a slow and steady loss of blood.
Maigret awakes the next morning in a local hospital, where he is at first put under close surveillance by the local authorities. The locality in which Maigret finds himself is Bergerac, which in recent months had been plagued by a so-called "madman" who would pounce upon unsuspecting women at night amid rustic surroundings, strangle them once he had them firmly in his clutches, and plunge a long needle into their hearts as a calling card. Maigret at first is thought to be this "madman" for he looked rather beat up when he was found, and had no personal ID on him. Thankfully, Leduc lives nearby, learns of Maigret's predicament, and is able to vouch for him to the satisfaction of the doctor, magistrate, and other local authorities.
This marks the beginning of Maigret's quest --- with the help of Leduc and Madame Maigret (who arrives from Alsace to help him get back on his feet, for he is facing a slow recovery) --- to investigate the case of this maniacal murderer who is the terror of this provincial town. At the same time, Maigret has to contend with the "obsessive snobbery and hypocrisy of small-town bourgeoisie" and their mistrust of him as an outsider. Certainly, Maigret's brusque, investigative style does nothing to endear him to Bergerac's denizens.
All in all, "The Madman of Bergerac" reads as an interesting moral, psychological tale with many twists and turns.