THE MANSION OF MADNESS

In 19th-century France, journalist Gaston LeBlanc visits a sprawling, remote psychiatric hospital in the mountains where a Dr. Maillard has purportedly invented revolutionary treatments for the mentally ill. Driven by carriage, Gaston is accompanied by his old friend Julien Couvier and Julien's cousin Blanche, and coach driver Henri. Julien, Blanche and Henri depart after being confronted by several aggressive, bizarre guards at the hospital's gated entrance, which terrifies Blanche.

Gaston meets Dr. Maillard and his beautiful niece, Eugénie. Gaston quickly observes that under Maillard's "soothing system" the patients of the hospital appear to roam free, acting in maniacal and at times violent ways, as well as engaging in religious cult-like activities, which Maillard encourages. Meanwhile, the carriage carrying Julien and Blanche is attacked by a gang of men who overwhelm the driver Henri, causing Julien and Blanche to flee into the woods on foot. Blanche is caught and brutally raped, and Julien is also captured and tortured by the men, but he eventually escapes, wandering the woods still tied up.

During his first night at the asylum Gaston has a hallucinatory dream and later accuses Maillard of being an imposter, abusing his patients as well as controlling Eugénie. Maillard responds that, despite her calm appearance, Eugénie is far more dangerous and violent than she appears. As Gaston observes the increasingly eccentric methods of Maillard's "soothing system", he begins to question the mental stability of the doctor. In the doctor's dungeon, innocent people are chained, tortured and stuck in glass cages, then forced to take part in gruesome games of ritual slaughter. Gaston escapes his quarters to search for Eugénie, who he witnessed taken away by guards into the woods. He finds and rescues her, discovering Julien along the way; however they are eventually all captured again by Maillard's guards. Julien finds Eugénie's father, the real Dr. Maillard, imprisoned with the driver Henri. The false "Maillard" is actually Raoul Fragonard, an inmate of the hospital who led a revolt and has imprisoned the staff and guards, replacing and impersonating them himself and his followers.

Fragonard organizes a ritualized Dionysian cult-like gathering with himself as the ringleader, where Gaston and Eugénie are sentenced to be executed by fire. Just before this happens, the original staff, including the real Maillard and Julien escape the prison and attack just moments prior to Gaston's execution. The escaped prisoners, led by the real Maillard take back control of the hospital. Fragonard is shot dead by Blanche, who declares "Viva la revolución" before killing him. Gaston, along with Julien and Blanche depart the asylum in the carriage they arrived in.

The real staff and doctors, aided by Julien, escape imprisonment and retake the asylum from the impostor Fragonard. Fragonard is shot dead by Blanche, and Gaston, Julien, and Blanche leave the institution.

The film concludes with order restored as the legitimate staff overcome the reign of madness imposed by Fragonard and his followers. Blanche's decisive act and the group's escape reinforce the fragile boundary between sanity and chaos, leaving the surviving outsiders to reflect on the ordeal as they depart the reclaimed institution.