An aristocratic young woman, Denise de Richemont, has murdered an important journalist, Jaques Le Tellier. She is acquitted by a sympathetic jury when she confesses it to be a crime of passion - revenge for the journalist's indiscreet revelation of his mistress' sordid family secrets.

But the real reason why Mademoiselle de Richemont killed Le Tellier is far more sinister, and Inspector Gautier pursues the case from the haute monde of fashionable Paris to the seething and dangerous slums, determined to solve the mystery behind the murder.