A phantom is up to mischief in the famous Louvre Museum in Paris. One night, during a tour of the portico in front of the statue of Belphégor, the Gautrais museum guard discovers a hooded figure. He fires several shots, but without hits. In the following night the security is strengthened. A few hours later, head warden Sabourel is found dead. Inspector Ménadier is conducting the police investigation. The young student André Bellegarde found out about the incident and wants to track down the ghost. He lets himself be locked in the Louvre at night. He meets the very attractive girl Collette, she is the daughter of the investigating inspector. Together they want to solve the mystery. Strange things happen in a dark atmosphere. The Phantom, now also known as Belphégor, appears and attacks Bellegarde. The wardens and policemen lying in wait are just in time to rush to the rescue. Again the phantom escapes. What was the background to this insidious raid? Who is behind the demonic mask? Can the riddle be solved at all? Episode 1 of the 13-part cult series in the Remastered Edition with resampled footage! With Yves Rénier and Juliette Gréco!