Judex

Favraux has amassed wealth through swindles and blackmail. He receives a threatening note signed 'Judex' demanding he return the swindled money to the victims. The note signals that Judex has begun watching him.

Favraux hires private detective Cocantin to keep an eye on things at the party where he plans to announce the engagement of his widowed daughter Jacqueline. Cocantin's presence is meant to deter trouble and keep Favraux safe. The party becomes a stage for Judex's unseen watchful presence.

Unbeknownst to the family, Alice's governess Marie Verdier is actually Diana Monti, a cat burglar. Favraux is smitten with her and she uses the situation to push for an engagement. She agrees to marry him for his fortune, only to murder him after the wedding to claim the wealth.

At the masked engagement party, a mysterious guest wearing a bird's head performs magic tricks. It is revealed that the magician is Judex, quietly watching over Jacqueline from within the crowd.

Favraux seems to die of a heart attack as he begins to announce his engagement to Diana. The guests fear foul play, while Judex's plan unfolds from the shadows. The apparent death sets the stage for Judex to act.

At Favraux's funeral, Jacqueline discovers a letter from Judex. She resolves that she will renounce most of her inheritance to spare Alice, accepting only a portion to ensure her safety.

Judex reveals that Favraux is not dead but drugged in a coffin. He removes Favraux from the coffin and imprisons him in an abandoned castle.

Diana makes several attempts to abduct Jacqueline, but Judex's vigilance foils each plan. The security around Jacqueline remains tight as Judex watches over her.

Diana also tries to abduct Alice, but this is foiled partly through Cocantin's efforts and Judex's orchestrations. The threat to Alice is neutralized for the moment.

Alive but despondent over losing Diana, Favraux commits suicide. The loss leaves Diana's plan unfulfilled and shifts the balance of power toward Judex and Jacqueline.

Judex's pursuit leads to a rooftop confrontation where Diana's accomplices are cornered. Daisy, a circus acrobat and Cocantin's ally, scales the building to confront Diana. The fight ends with Diana's death.

Judex and Jacqueline are finally reunited and walk along a beach as their story closes. The partnership between justice and conscience is reaffirmed in a serene final moment.

The film ends with a title card paying homage to Louis Feuillade and remembering a time that was not happy: 1914. The memory underscores the moral weight of Judex's vigilante justice.