Maigret comes under pressure from his superiors and the press to catch a serial killer of women with no common feature except their hair. Making no progress Maigret sets a trap using undercover police women. The trap yields a clue to a suspect with a possessive wife and mother but a sixth murder while his suspect is in custody throws doubt on Maigret's theory and his superiors decide to replace him as investigator of the case.

One morning, an agitated man calls the Police judiciaire asking for Maigret. He claims he's being followed by someone trying to kill him. Before Maigret can get the details he hangs up, calls back again from various cafés, until the calls finally stop. That night, his body is found, his face badly beaten, stabbed to death. Ridden with guilt for not having saved “his" dead man, Maigret is determined to find the murderer.