Dr. Henry Foustka

Dr. Henry Foustka is a dedicated scientist working at the Institute, a scientific research facility. Despite his professional role, he is secretly drawn to the occult, often found alone in his study, lighting candles and chanting incantations. Foustka embodies a Faustian figure, torn between his scientific pursuits and the darker arts, suggesting that science might be akin to devil worship. He employs the services of Fistula, whose arguments force Foustka to confront his own convictions. Ultimately, Foustka falls victim to Fistula's accusations, vanishing in a mystical cloud of smoke.

Fistula

Fistula is a retired invalid with a sinister and philosophical bent, frequently visiting Foustka uninvited. As the Mephistopheles-like figure in the narrative, Fistula plays a pivotal role in undermining Foustka. He expertly manipulates Foustka into confessing beliefs he doesn't actually hold, only to later betray him to the Director. Acting as an agent provocateur, Fistula's influence leads to Foustka's downfall.

The Director

The Director is the authoritative head of the Institute, perpetually in search of supportive staff and subservient associates. Despite a peculiar attraction to Foustka, his proposition for a closer relationship is rejected. The Director exemplifies malevolence, camouflaged by a veneer of concern for others and a self-effacing demeanor. His actions towards Foustka reveal his manipulative and deceptive nature.

Vilma

Vilma, also a scientist and Foustka’s lover, is deeply involved in elaborate role-playing scenarios within her romantic life. She faces accusations from Foustka of being complicit in his exposure to the Director. Disillusioned by Foustka’s deceitful behavior, Vilma loses her respect for him. Eventually, she enacts one of her long-held fantasies, beginning a relationship with a dancer who gifts her with violets each night.

The Deputy Director

The Deputy Director is characterized by his oily and hypocritical demeanor. Although he serves as the Director’s spokesperson, he is secretly despised by him. As a facilitator for the Institute, he is always accompanied by a silent girl named Petruska, who clings to his hand unless she discreetly slips away to engage in affairs with other scientists.

Maggie

Maggie, an attractive and youthful secretary, is entirely captivated by Foustka's persuasive rhetoric. She develops a romantic infatuation with him, viewing him as a valiant opponent of the devil. In her devotion, Maggie sacrifices her position to defend him when he faces condemnation from the Director. Her world unravels, leading to madness, when the Director dismisses her for her unwavering support of Foustka.

Lorencova, Kotrly, and Neuwirth

Lorencova, Kotrly, and Neuwirth are staff scientists at the Institute, entangled in various romantic liaisons. They serve as the jury during Foustka’s metaphorical "trial" and are frequent attendees at the Institute's social gatherings. Their involvement underscores the intricate social dynamics and political machinations within the Institute.

Mrs. Houbova

Mrs. Houbova is the elderly landlady of Foustka, representing the unpretentious and straightforward aspects of the real world. Her interactions with Foustka are marked by sanity and protectiveness, while she instinctively feels repulsion towards Fistula, highlighting her intuitive nature.