In the Belle Époque era, a captivating young woman named Marie, known as Casque d'Or because of her golden hair, becomes enmeshed in a tragic love triangle. She is initially linked to a volatile gangster named Roland, but her life takes a dramatic turn when she meets Manda, a reformed criminal who now works as a carpenter. Their mutual attraction is immediate and undeniable, eventually leading Manda to confront the criminal underworld from which he has tried to escape. As their passion intensifies, tensions rise, and Manda finds himself drawn back into a dark and dangerous life he had hoped to leave behind.

As Manda and Marie's love blossoms, they face relentless opposition from Roland and his cohorts as well as the broader criminal network controlling the Parisian underworld. Their struggle for happiness pits raw emotion against the harsh realities of their circumstances, evoking themes of loyalty, betrayal, and the cost of freedom. As fear and danger intensify, Manda must confront his past and make impossible decisions, setting in motion a series of events that will irreversibly alter the course of their lives.