The rich, amoral Zelie is married to Pierre Boucheron, "The Rat" - but her interest in another man is an open secret. Forced to defend his honour, the Rat takes refuge in his old domain of the Paris underworld. But even here he has a rival - and when murder is afoot, the sinister Morel's ambition threatens to cost the Rat dear....

Pierre Boucheron, alias 'The Rat' and a former underworld notoriety, is now living the high life as the kept man of Zelie de Chaumet. But when she learns he is planning to marry another woman, her vengeance pursues him into the murkiest depths of Paris...

When bored courtesan Zelie de Chaumet begs her lover, the corrupt and powerful Stetz, to take her slumming, the pair encounter Pierre Boucheron, alias 'The Rat' , boy-king of the Paris underworld, and the innocent Odile. Love, life and jewels are risked and lost in this powerful romantic melodrama as the four characters' lives are changed by this chance encounter for ever.