Maigret Sets a Trap

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?