A young American ballet student named Suzy Banyon (Jessica Harper) travels to Germany to enroll in a renowned dance academy, filled with anticipation and excitement. However, her arrival coincides with a violent downpour, an omen perhaps of the sinister events yet to unfold. As Suzy approaches the imposing structure of the school, she witnesses a distressed young blonde girl, Pat Hingle (Eva Axén), fleeing in sheer terror. The girl's desperate cries echo against the backdrop of the thunder, but before Suzy can comprehend the situation, Pat disappears into the stormy night.
Upon her efforts to enter the academy hindered by a dispassionate voice from the intercom, Suzy is left with no choice but to retreat back into a cab. As they drive away through the dense forest, she spots Pat running frantically among the trees, an image that will haunt her. At that very moment, Pat seeks refuge at a friend's apartment, but her nightmare escalates when a terrifying entity catches her eye. In a chilling encounter, she is seized by an ominous arm that smashes through the window, leading to a gruesome unraveling of events that ensues. Pat's fate is sealed as she is violently attacked and subsequently meets her end, a sinister prelude to the horrors that will plague Suzy and her fellow students.
The following day, Suzy finally gains access to the academy, greeted by Ms. Tanner (Alida Valli) and the seemingly benevolent Madame Blanc. Supportive to Suzy upon recognizing a familial connection, Madame Blanc embodies a facade that belies the darkness lurking within the institution. As Suzy navigates through the initial shock of a murder investigation and disquieting occurrences at the school, she encounters several peculiar characters, including the ominous handyman, Pavlo, and the blind pianist, Daniel (Flavio Bucci).
In the changing room, she meets her fellow classmates, Olga (Barbara Magnolfi) and Sara (Stefania Casini). A strange dynamic exists between the two girls, tinged with jealousy and secrets, and as Suzy discovers her living arrangement with Olga, she becomes increasingly troubled by Pat's mysterious fate. Paired with Olga, Suzy hears disconcerting rumors about Pat, which ignite a sense of curiosity and apprehension within her.
As she adjusts to life at the academy, strange incidents plague the students. Disturbances escalate into horror when Suzy is besmirched by a falling mass of maggots, followed by the unnerving discovery that the teachers may not be who they claim to be. At night, while the girls slumber, the fearful sound of a raspy snore reverberates through the corridors, instilling dread in their hearts as they ponder the possibilities of what lurks behind closed doors.
The tension culminates when Sara uncovers a sinister secret—her notes detailing alarming occurrences mysteriously vanish, sending her into a tailspin of terror and paranoia. It soon becomes apparent that the very academy designed to nurture talented dancers harbors dark secrets and even darker forces. Sara's desperate attempts to protect herself lead to haunting revelations; however, her fate becomes entwined with a traumatic end that Suzy can only witness, solidifying the threat surrounding them.
With the students mysteriously disappearing one by one, Suzy's determination to unveil the truth heightens. An encounter with Sara's psychologist reveals the haunting lore of Helena Markos, the academy's founder, who was long rumored to be a witch. It becomes clear that Suzy is not merely fighting for survival; she is in a battle against ancient, malevolent powers that seek to ensnare her within their lethal grasp.
In a gripping act of courage, Suzy uncovers the connection between Pat's last words and the secrets of the academy. As she delves deeper, she stumbles upon a coven's clandestine assembly led by Madame Blanc, who now reveals her true colors. The sinister ritual involving Helena's dark powers threatens to consume Suzy, demanding a sacrificial offering amid the shadows of the school.
As the tension reaches its zenith, Suzy, armed with newfound resolve, confronts Helena. In a chaotic showdown where the lines between good and evil blur, Suzy discovers the extent of her own strength and the price of survival. The climactic confrontation results in a powerful explosion of magic and fury, leading to Helena's demise amidst a maelstrom of chaos.
As the school crumbles around her, Suzy emerges into the storm, possibly inheriting the very darkness she sought to escape or perhaps finding liberation in her victory. With the academy ablaze behind her, she walks away with a mysterious smile, leaving the audience pondering whether she has truly escaped or become entangled in an even greater fate tied to the world of witchcraft that once ensnared her soul.
