In 1700 in Nevers, France, a skilled swordsman named Lagardère [Daniel Auteuil] challenges Duke of Nevers [Vincent Pérez] to a friendly duel to learn a secret lethal maneuver known as the "Nevers Attack." Lagardère demonstrates swift skill, and though Nevers is unflustered by the challenge, the encounter quickly turns into an unexpected friendship. From this new bond, Nevers uncovers a hidden truth: he has a child with Blanche de Caylus [Claire Nebout], a revelation kept secret for years by his cousin and would-be heir, the scheming Comte de Gonzague [Fabrice Luchini]. That same night, Nevers narrowly escapes an assassination attempt staged by Gonzague’s men.
Determined to secure his bride, Nevers travels toward Caylus with Lagardère at his side as escort. Gonzague and his men pursue them, aiming to murder Nevers before he can wed Blanche and claim his supposed heir. Along the journey, Nevers passes on the Nevers Attack—an acrobatic feint that ends with a blade between the opponent’s eyes. When the assassins finally close in, Lagardère buys enough time for Nevers to reach Caylus and marry Blanche. The union, however, promises little happiness for long.
When Gonzague and his men arrive at Caylus, they murder the entire wedding party. Lagardère reaches the scene just in time for a lengthy sword fight; Nevers is fatally stabbed by a masked Gonzague, who is branded on the hand by Lagardère’s blade. With his dying breath, Nevers pleads for vengeance and asks Lagardère to safeguard their infant child. Lagardère flees Caylus with the baby and finds refuge in a mountain farmhouse, where a whispered truth emerges: the “son” is a girl, and a locket naming her Aurore confirms her identity [Marie Gillain].
Gonzague’s hunters press the pursuit, but Lagardère and Aurore slip away with the help of a band of strolling players who convince their pursuers that Lagardère and Aurore have fallen to their deaths in a mountain torrent. Back in Nevers, Blanche mourns what she believes to be the loss of her daughter and withdraws to a convent, while Gonzague is named the executor of her estate.
Sixteen years pass. Lagardère and Aurore remain with the troupe, practicing their swordplay and shielding secrets about their past. When Aurore learns more about Lagardère’s history, he quietly teaches her the Nevers Attack, forging a bond that blends danger with hope. After a party hosted by Gonzague’s ally Louis-Joseph, Aurore is assaulted, but she escapes using the same technique she learned, even killing her attacker in the process.
Gonzague’s suspicions grow—he fears Aurore still lives. He opens a tomb that reveals only a decayed wax doll, confirming his worst fears. Lagardère, meanwhile, crafts a plan to secure Aurore’s true heritage: he reveals that she is the daughter of the late Duke of Nevers and that her mother may still be alive. Disguised as a hunchback, Lagardère infiltrates Gonzague’s circle and reestablishes contact with Blanche, who confirms that her daughter is indeed alive. He then orchestrates a bold stock market raid on Mississippi Company shares, using Blanche’s funds to secure Aurore’s future.
When Aurore is captured by Gonzague’s men, Lagardère executes a daring rescue. The Regent Philippe d'Orléans arrives with plans to name Gonzague a royal agent to Louisiana, but Lagardère interrupts the ceremony, presenting Aurore as the majority holder of the Mississippi Company stock. Blanche confirms that Aurore is her daughter, and Lagardère sheds his disguise to publicly accuse Gonzague of murdering Duke Philippe de Nevers. In the climactic duel, Lagardère kills Gonzague using the Nevers Attack, and Aurore invites him to seal their union with a kiss as they embrace, hopeful about the future they may forge together.
