A stripper in Montmartre reports that she had last night overheard two men at her club planning to kill a countess. Her report is taken but as the crime has not happened not much attention is paid to her claims until a few hours later, when she is found in her room, strangled to death. And the next day the Countess, a drug addict, is found strangled. Maigret is bought in to find the link between the victims and bring the killer to justice.