In Paris during the Regency, we meet Henri, a young acrobat and swordsman nicknamed “Le petit parisien,” trained by Cocardasse and Passepoil. The court is abuzz with talk of the “trois Philippe”—d'Orléans, Gonzague, and Nevers—and rumors of a secret daughter born of the love between Nevers and Blanche de Caylus. While Lagardère proves himself for the first time, Gonzague's ambitions take shape and foreshadow the coming conspiracy, though it has not yet erupted.

Lagardère, wrongly accused of the Nevers'murder, flees with little Aurore to protect her from Gonzague. Hiding under a false identity, he raises the girl in secret, far from Paris, while Gonzague, convinced that she is still alive, mobilizes his spies to find her.

The court of Philippe d'Orléans is decked out in its finest attire for an evening that appears brilliant on the surface, but is teeming with intrigue. Under the chandeliers and masks, Lagardère slips among the guests, listening intently to every conversation in search of clues about the assassination of the Duke of Nevers. Philippe de Gonzague and his allies work in the shadows, concealing their maneuvers behind feigned politeness.

Henri de Lagardère, still disguised as a hunchback, attends the wedding organized by the Prince of Gonzague and, taking advantage of his anonymity, observes and listens, gathering evidence against Gonzague and his accomplices, including Peyrolles. At the crucial moment, he interrupts the ceremony, reveals his true identity, and publicly confronts his enemies.

Henri de Lagardère continues to follow the trail of Aurore de Nevers, whom the Prince of Gonzague's men are trying to smuggle into Spain to remove her from any protection. The chosen route is the Poncarbo Pass, a narrow and isolated mountain pass, ideal for a discreet transfer.

After following and thwarting the Prince of Gonzague's schemes throughout his journey, Henri de Lagardère knows that the time has come to fulfill his oath: to avenge the death of Philippe de Nevers and restore Aurore's inheritance.