The creeping black assassin Fantômas, the criminal lord of Paris and master of disguise, has won the first round. But the equally resourceful Inspector Juve swears to win the second.

Naturally, after his last experience, Inspector Juve winces under such rebuff as the substitution of Valgrand and the escape of Fantomas. Eventually a mysterious crime puzzles him and his assistant, Fandor. To the chief of the Criminal Investigation Department, he reports that the body of a woman, found in the house of Dr. Charles, cannot be identified. Papers bearing the name of Lady Beltham had been discovered in her clothing. Was the body that of Lady Beltham, the accomplice of Gurn, or was it the intention that people should believe that she was dead? Juve wondered why the body was found in the house of Dr. Charles. He concerns himself to watch the house, and the patience of Fandor and himself is unexpectedly rewarded. One day Dr. Charles leaves the house, and the car in which he rides is followed. Charles makes a false move. The man who leaves the closed car is not the Dr. Charles who got in. He is now a young man, with a black moustache, whereas Charles is a middle-aged man with a black beard. That is decidedly suspicions, and the detectives are in time to see him accept a note from a woman who is waiting for him. Instructing Fandor to follow the girl, Juve goes after the other man, known to the police as Lawrence, the leader of bandits. Following Lawrence (alias Charles) in a taxi, he is fated to lose his quarry, as an accomplice of the bandit punctures the tire of one of the wheels, and Juve is stranded in a street while Lawrence gets clear away. So far there is nothing to connect Charles, alias Lawrence, with Fantomas, alias Gurn. Fandor fares much better. The girl does not succeed in throwing the younger detective off the track and is apparently unconscious of the fact that she is being followed until she notices Fandor in the same compartment of the railway carriage in which she is traveling. Fandor tracks her to a house. Having seen her safely indoors, he sends a note to Juve, saying that he is keeping a good watch. Meanwhile, Lawrence has rend the note Josephine handed him, and he learns that an elderly man, confidential clerk in the employment of Messrs, Brown and Co., has fallen in love with her. That afternoon he is taking $30,000 to clients of the firm, and thinking that she is attached to him, wishes to take her with him on the journey. They were leaving the Gare de Lyon Station for Bercy by the Northern Express at three o'clock that afternoon. Would Lawrence be at the station with others of the gang? In consequence of the breakdown of the car, the note which Fandor had written did not reach Juve. Fandor, however, had waited near the house of the girl, and when she left, dressed as a lady, followed her to the Gare de Lyon, where she met the confidential messenger. No doubt there was a hidden meaning in this meeting, and Fandor decided to join the train; so did Lawrence and others of the gang whom he had gathered round him. The whole party traveled in the last coach of the train, and when the time bad arrived, one of the men climbed along the footboard and uncoupled the coach. Lawrence recognized Fandor, but his presence on the train made no difference to the plans of the bandits. As the coach began to fall away from the rest of the train, Josephine left the compartment in which a peremptory demand for the money be carried, whilst Fandor was also attacked. By this time the speed of the coach has very sensibly slackened and the gang easily escaped, fleeing in a motorcar waiting for them. In the car they examined the haul, and to their intense mortification discovered that the notes the man carried were all half notes, the remainder of which were to be handed to the clients of Brown and Co. when the contract was completed. When Fandor recovered from the shock of the attack he pulled the communication cord. To his consternation he found that not only had it been severed, but that the coach was running down the decline. He knew that the Northern Express was following the train in which he had traveled, and nothing but a miracle would avert a serious disaster. The coach ran back, and as the express began to cross the bridge the engine collided with the coach and the whole train was terribly wrecked. Lawrence determines to obtain the remaining halves of the notes, but decides that before doing so Juve must be killed. With that purpose in view, he, in the name of Fandor, wires to Juve to come to the Bercy cellars of Brown and Co. the following night. Juve, taking the wire as authentic, goes to Bercy, and. seeing someone moving behind the casks, fires, and then creeps forward, to run against Fandor. Lawrence and his accomplice began firing at the detectives, the barrels of spirit were set on fire, and through a tornado of flames the detectives escape. Fantomas again himself escapes, and they lose entire trace of him until one night when at a hotel, Juve and Fandor meet Josephine, and after Juve is introduced by Fandor, he insists that Josephine divulge the whereabouts of Fantomas. She reluctantly, under the threat of arrest, takes Juve to a place where Fantomas is dining with two wealthy young ladies in the disguise of the supposed Dr. Charles. A card is sent to Fantomas saying that someone is waiting for him outside. Fantomas, believing this to be one of his gang, departs from the hotel and is immediately arrested by Juve and Fandor. After they walk down the street, Dr. Charles suddenly makes a struggle and to the amazement of Juve and Fandor, he leaves in their hands nothing but two plaster casts of his arms with his coat sleeves attached. They decide to track Lady Beltham. After much trouble they discover her to be making midnight visits to her old haunted villa. Here they make a visit in the day-time, and being satisfied that there must be still some connection between Fantomas and Lady Beltham, hide and overhear a conversation where Faniomas decides be must get rid of Juve and will send a silent executioner to destroy him. Juve does not exactly know what this silent executioner means, but he prepares to receive a serpent. He is almost crushed to death in spite of his precaution, but survives and surrounds the haunted villa of Lady Beltham. Fantomas is almost caught unprepared, but being ever ready, he quickly sets a trap in which to get together the whole of the police, including Juve and Fandor, so that he may destroy them all by dynamite. These easily fall into the trap, so quickly but well laid. Fantomas realizes that his opportunity has come, and leaping from a cistern in which he had been hiding, he touches the coil of wire and explodes the dynamite cartridge, blowing the haunted villa to a heap of ruins, together with the occupants. The question still remains unsolved: Are Juve and Fandor still alive?—Moving Picture World synopsis