Tony "le Stéphanois," played by Jean Servais, is a seasoned criminal who has recently been released from a five-year prison stint after serving time for a daring jewel heist. Upon stepping back into the streets of Paris, he finds himself struggling with misfortune and a sense of disillusionment. His life takes a turn when his old friend Jo, played by Carl Möhner, approaches him with a risky proposition: a bold smash-and-grab that would target a jewelry store's window during broad daylight. The plan involves breaking the glass of a Parisian jeweler's storefront and quickly grabbing some precious gems. However, Tony initially refuses to participate, wary of the dangers involved.
Soon after, Tony learns that his former girlfriend, Mado, played by Marie Sabouret, has moved on during his absence and is now involved with a powerful gangster, Pierre Grutter, portrayed by Pierre Grasset, who owns a nightclub in Paris. Finding Mado working at Grutter’s club, Tony decides to see her again, bringing her back to his modest, run-down apartment. It’s evident that she is well-maintained despite her current situation, which provokes Tony's anger about her ties with Grutter. In a moment of rage, he beats her for her deep involvement with the gangster, revealing the complicated and often dangerous lives they all lead.
Eventually, Tony’s attitude toward the heist shifts. He agrees to take part, but with an ambitious twist: instead of only stealing from the window, they plan to rob the store's safe, which is a much more complex and lucrative task. Mario Ferrati, played by [Robert Manuel], suggests they bring in César, a skilled Italian safecracker played by [Jules Dassin], to help with the job. Together, the four men craft an intricate plan to break into the store, carefully disabling its sophisticated alarm system. Their operation begins on a Sunday night, with the crew chiseling through a cement ceiling from an upstairs flat, proceeding methodically and quietly to avoid detection.
The climax of their plan is tense and suspenseful, as they carry out the daring break-in. They successfully make their way into the store, and the police seem none the wiser as they escape, leaving behind no identifiable clues. However, César secretly pockets a diamond ring as a present for his lover, Viviane, a chanteuse at Grutter’s club, played by [Magali Noël]. This small act of theft will have unforeseen consequences. The stolen jewels are quickly fenced in London, adding an international layer to the crime.
Meanwhile, the fallout begins to unfold. Grutter, having seen Mado battered and distressed, cuts ties with her. Infuriated by Tony’s interference in his life and doubting his loyalty, Grutter, portrayed by [Claude Sylvain], orders his brother Rémy, played by [Robert Hossein], to kill Tony. But Louis Grutter, played by [Pierre Grasset], uncovering César’s gift to Viviane, realizes that their friends Tony, Mario, and César are responsible for the jewel theft. Grutter forces César to confess, and despite the tempting police reward of FF10 million, Grutter decides to take matters into his own hands.
In a brutal turn, Grutter’s henchmen murder Mario and his wife, [Fredo’s Wife] played by [Marcelle Hainia], because they refuse to reveal the whereabouts of the stolen loot. Tony, ever resourceful, retrieves the jewels from Mario and Ida’s apartment and anonymously arranges a funeral for the couple. Driven by revenge and a desire to protect his own, Tony seeks out Grutter, finding César in captivity and ultimately exposing him. In a tragic culmination, Tony, adhering to a code of honor, kills César after he confesses to having squealed on the gang.
The story takes another dark turn when Grutter’s men kidnap Jo’s young son, Tonio, holding him for ransom. The ransom is delivered by a London contact, and Tony, realizing that the boy's life is at stake, decides to personally rescue him. With the help of Mado, Tony tracks the child to Grutter’s country estate. In a fierce and violent confrontation, he kills Rémy and Louis to free Tonio and escapes with the child. On their journey back to Paris, tragedy strikes again: Jo, overwhelmed by the mounting pressure, agrees to meet Grutter with the ransom money. Tragically, when Jo arrives, Grutter reveals that Tony has already taken the boy, and in a final act of violence, Krutter kills Jo.
The battle reaches its climax as Tony, wounded and bleeding, confronts Grutter at his residence. Despite his injuries, he manages to kill Grutter as the gangster attempts to flee with the stolen jewels and cash. Injured and exhausted, Tony drives desperately back to Paris, determined to save Tonio. He manages to deliver the boy safely before succumbing to his wounds and passing away as police and bystanders gather around him. In his final moments, Tony’s sacrifice is clear as he ensures the safety of his friend’s son, carrying a suitcase filled with FF120 million in cash — a symbol of his final act of loyalty and desperation.
In the aftermath, Jo’s wife, Louise, leaves her child and the scene, taking her son away, and leaving the suitcase and Tony’s body for the police. The story ends on a somber note, highlighting themes of loyalty, betrayal, and the high cost of a life lived on the edge of legality.
