The Man Without A Face is a daring criminal who can assume disguises as readily as Sherlock Holmes. No-one knows what he really looks like, not even the woman who loves him and is his partner in crime. Who would suspect Mademoiselle Ermance, a quiet lady who sells sewing accessories? Yet this demure disguise conceals the red-masked leader whose ruthless gang he controls from an underground hide-out. Another accomplice, Dr Dutreuil, can reduce people to robots and command them to kill those victims he chooses for them.

The Man Without A Face is searching for the lost treasure of the Templars. He tries to wring the secret from historian Maxime de Borrego, but the old man dies without talking. The master criminal assumes the identity of his victim in order to continue the search. He is discovered by the historian's nephew, Paul de Borrego, but he escapes after locking up Inspector Sorbier, Paul de Borrego and his servant Albert, in a room filled with gas. They are saved in the nick of time, but the next day Dr Dutreuil's robots murder Albert within police headquarters itself.

The woman attempts to capture Paul in a taxi driven by remote control, but she fails and is caught in a trap set by a private detective, Seraphin Beauminon, who used Paul's friend, Martine Leduc, as a decoy. She is captured by Sorbier and his men after a perilous rooftop chase, but The Man Without A Face intervenes and rescues her.

Paul and Seraphin just escape the human robots sent by The Man Without A Face, who has been attempting to steal the Templars' documents in Maxime de Borrego's collection. After dazzling acrobatics on top of an express train at night, the criminal finally gets his hands on the documents. But he discovers that they are forgeries. Professor Petri, who had guaranteed their authenticity, is executed by the robots. The Man Without A Face captures Paul, Martine and Seraphin and hands them over to Dr Dutreuil, but they are saved by the Templars, moments before the arrival of the police.

But the villain and the woman have disappeared. Meanwhile Mademoiselle Ermance and her delightful niece say goodbye to a regular customer in their shop. They are going away for a short rest. . . .