Vidocq

In 1830 Paris, Vidocq corners the Alchemist in a glass factory's furnace room. During a heated fight, the Alchemist pushes Vidocq into the blazing furnace. Hanging onto a ledge, Vidocq pleads for the killer to reveal his face, and the Alchemist obliges. Vidocq lets go and falls into the fire.

Vidocq's fall leaves his fate uncertain and those around him believing he perished. The case pushes forward as journalist and colleagues vow to uncover who killed him and why.

Journalist Étienne Boisset visits René Nimier's office to help write Vidocq's biography. He also expresses a plan to uncover Vidocq's murderer and the hidden network behind his downfall.

Lautrennes, Paris's chief of police, orders officer Tauzet to investigate Vidocq's death. He cautions that the political climate is unstable and that getting the truth could be dangerous.

Belmont and Veraldi die in a supposed lightning strike at their cannon factory. Investigators notice powder on a worker's clothes that catches fire, and a servant confesses to receiving a cash-filled letter ordering him not to clean the jackets. Realizing the 'lightning' is being manipulated, the team spots metallic pins inserted into the victims' hats.

Boisset retrieves the pins from Nimier's office and traces their design to Preah, a dancer in a brothel and Vidocq's lover. Vidocq also locates Preah and learns that she received a letter offering money to place the pins in Belmont and Veraldi's hats.

Vidocq rushes to save Ernest Lafitte, owner of an orphanage, but the Alchemist arrives first and appears to wield magical powers. The confrontation hints at a larger, supernatural plan behind the killings.

Boisset's investigation leads him to Sylvia, Froissard, and Marine Lafitte, who reveal that Lafitte, Belmont, and Veraldi sought youth by making deals with the Alchemist. The three rich men agreed to cooperate in capturing maidens for experiments but later felt guilt and withdrew. In response, the Alchemist killed them.

After Boisset leaves, the Alchemist arrives and kills Froissard and Marine. Tauzet notices the killer disposing of witnesses and fears Boisset will be next.

Boisset retrieves Vidocq's notes, which describe a lab where the Alchemist uses maidens' blood to create a substance for his mask. The mask allegedly grants eternal youth by siphoning souls. The Alchemist attacks Vidocq during this revelation, and Vidocq manages to take a shard from the mask before the killer escapes.

Vidocq's final note states that the mask will need to be manufactured, guiding Boisset, Nimier, and Preah toward the glass factory. They enter the building, following the trail of clues.

Inside the factory, an artisan guiding the group removes his prosthetic and reveals himself to be Vidocq. He explains that he faked his own death to mislead Boisset and lower the killer's guard.

The group discovers that Boisset has been masquerading as the Alchemist. Nimier tries to shoot, but the Alchemist surprisingly reflects the bullets back and kills Nimier.

Vidocq chases the Alchemist into a hall of mirrors and forces him to look into a shattered mirror piece. The trapped souls within the mask are freed, and Vidocq impales the Alchemist with the shard before tossing him into the river.

At Nimier's funeral, the Alchemist's menacing laugh echoes in the distance, accompanied by a glimmer of his mask. The question of whether he is truly dead remains unresolved.