Maigret is visited by Ernestine, the wife of a burglar known as 'Sad Freddie'. Whilst breaking into a house he discovered a body and is so alarmed he has fled the country. The trail leads Maigret to a dentist who lives with his domineering elderly mother. His wife has gone missing but Maigret needs to find a body if he is to provide a link.
Maigret is called to investigate a murder in a small village near to La Rochelle, the victim being old Jeanne, shot through her window. She was the local post mistress with access to everyone's mail and knew everyone's secrets. The main suspect is a married school-teacher but the local doctor explains to Maigret that this is chiefly because he has come from Paris and the village resents in-comers. A chat with two school-boys puts Maigret in the right direction.
An elderly widow is sure someone is following her and entering her flat when she's away. Maigret assumes she is having senior moments and assigns a subordinate to escort her home. When the woman is found smothered to death, the detective is plagued with guilt and vows to apprehend her killer. The only suspects are her only relatives: her middle-aged daughter who disliked her mother, her paid gigolo, and her wastrel grand nephew who sponged off the victim.
Maigret receives an anonymous note announcing that a crime will be committed during first mass at the rural church in his provincial home town. Unable to resist the temptation, the detective attends the service and finds that the countess whom his late father worked for as bailiff has died from a heart attack. When he discovers that a bogus news article falsely announcing her son's suicide in her prayerbook, Maigret correctly assumes that foul play was involved.
A serial killer is murdering young women in Paris. Maigret sets a trap using a policewoman as a decoy in the murder location. The killer attacks her but when the police come he runs away, leaving a sartorial clue which links to Marcel Moncin, a married mother's boy. Maigret arrests Moncin but whilst he is in custody there is another killing. Has Maigret got the wrong man or does Moncin have an accomplice?
The beautiful wife of American businessman Oswald Clark is found strangled in a kitchen locker in the posh Majestic Hotel in Paris. Maigret notes that the murdered woman arrived at her fatal meeting armed with a pistol and discovers that not only is Clarke having an affair with his son's governess, but that the son's paternity is in question.
Answering a desperate phone call from a young lady in distress, Maigret finds the drunken young woman in a sleazy bar. The detective chivalrously checks her into a respectable hotel and returns home to complete his interrupted night's sleep. When he reports to work, he finds that the young woman has concocted a charge of attempted rape and finds himself the subject of disciplinary action. Maigret suspects his pursuit of a gang of restaurant thieves is the impetus for this accusation and with the help of his loyal staff, he is able to find the ultimate answer in a dentist's chair.
Leon Florentine, an old school acquaintance of Maigret, shows up at the detective's home asking for help in the shooting death of his mistress. Maigret has only obvious distaste for the unkempt, disheveled Leon, who has survived since boyhood by sponging, lying, and conning his way through life. Although the dead woman allowed him to live with her rent free, her busy social life included four other lovers, all of whom were unaware of the other's existence. When they were scheduled to arrive, Leon would discreetly leave the apartment, but if they arrived unexpectedly, he would perversely hide in the wardrobe. The plot becomes even more complicated when Maigret finds out that Leon was in the wardrobe when the murder was allegedly committed.
Maigret is called in the middle of the night by the Minister of Public Works to discreetly conduct an unofficial investigation into the theft of an engineering report from his office. The paper was written years earlier and correctly predicted the collapse of a sanatorium which killed 62 children. The high death toll puts everything and everyone connected with the building's construction under suspicion and the resultant scrutiny threatens to topple the government. Maigret correctly suspects the theft to be an inside job with politically-motivated ramifications.
