Suzy Bannion travels to Germany to perfect her ballet skills. She arrives at the Tanz dance academy in the pouring rain and is refused admission after another woman is seen fleeing the school. She returns the next morning and this time is let in. She learns that the young woman she saw fleeing the previous evening, Pat Hingle, has been found dead. Strange things soon begin to occur. Suzy becomes ill and is put on a special diet; the school becomes infested with maggots; odd sounds abound; and Daniel, the pianist, is killed by his own dog. A bit of research indicates that the ballet school was once a witches' coven - and as Suzy learns, still is.
An American dancer, Suzy, is about to attend a prestigious ballet school in Germany. No sooner has she arrived than another student at the school is brutally murdered. Sinister deeds are afoot and Suzy starts to think that the school houses something evil.
A young American dancer travels to Europe to join a famous ballet school. As she arrives, the camera turns to another young woman, who appears to be fleeing from the school. She returns to her apartment where she is gruesomely murdered by a hideous creature. Meanwhile, the young American is trying to settle in at the ballet school, but hears strange noises and is troubled by bizarre occurrences. She eventually discovers that the school is merely a front for a much more sinister organization.
A newcomer to a prestigious ballet academy comes to realize that the school is a front for something sinister amidst a series of grisly murders.
- A young American ballet student, Suzy Banyon (Jessica Harper), flies to Germany to attend a prestigious dance academy. On the night of her arrival there is a torrential downpour. She arrives at the school by taxi, and before she can enter, she witnesses a young blonde girl (Eva Axén) fleeing the building in a panic. Suzy hears the girl shouting to someone just inside the door of the school, but the intense thunder obscures most of her words. When the other girl is gone, Suzy talks to an unidentified person on the school's intercom, but they refuse to let her inside. Unable to gain access to the school, Suzy gets back into her cab and has the driver take her away. As the cab drives through a nearby forest, Suzy sees Pat running alone through the trees that separate the school from town.
The frightened girl is Pat Hingle, and she flees to a friend's apartment in the nearby town. While alone in the bathroom, she becomes transfixed by a pair of shining eyes outside the window, and a decidedly inhuman arm smashes through the glass, grabbing her. She is pulled out of the window onto the roof, stabbed numerous times, and then hanged by a cord when she falls through the sky light. The huge pieces of glass and metal that break out of the skylight fall on Pat's friend, killing her by impaling her body and her head in numerous places.
Suzy goes to the school the next day and is greeted by Ms. Tanner (Alida Valli), an instructor, and Madame Blanc (Joan Bennett), the vice directress. Madame Blanc is very friendly to Suzy, especially when she realizes she knows Suzy's aunt Carol. Detectives are there investigating Pat's murder, and although Ms. Tanner tries to hurry Suzy away, Suzy volunteers a few bits of information. It seems as if there is something that she cannot remember, some realization that she can't put her finger on. Suzy meets a few other odd characters, including a strange looking handyman named Pavlo (Giuseppe Transocchi) and a blind pianist named Daniel (Flavio Bucci).
In the changing room, Suzy meets two other students, Olga (Barbara Magnolfi) and Sara (Stefania Casini). Sara and Olga are not friends, and Olga taunts Sara a little. Although Suzy has requested to board at the school, the rooms are all full and it's been arranged for Suzy to live with Olga in her off-campus apartment. Although Olga initially seems very bitchy, she and Suzy get along well and have a conversation about Pat. Olga tells Suzy that Pat was a "busybody", and that she was always trying to find out things about other people. Suzy thinks back to seeing Pat the night before, and she suddenly remembers Pat shouting the words "secret" and "iris".
The next day, Suzy sees Madame Blanc before classes, and she tells Suzy that her dorm room is now free. Suzy, however, tells Madame Blanc that she'd rather live with Olga. Madame Blanc seems offended by this and walks away in a huff. Ms. Tanner sarcastically tells Suzy that she is happy she's so "strong willed". On her way to class immediately afterwards, Suzy passes by the cook, who is sitting in the hallway with Madame Blanc's small nephew Albert (Jacopo Mariani). The cook is polishing some silver, and she reflects a beam of sunlight at Suzy, who immediately begins to feel ill. In class, Ms. Tanner keeps pushing Suzy to dance, and Suzy passes out, bleeding from her nose and mouth.
The school doctor (Renato Scarpa) puts Suzy on a restricted diet that includes cheese, fruit, and a glass of red wine. Suzy also finds that she's been moved into the dorms without her consent. Her dorm room is next to Sara's, and the two of them become friends. As the girls dress for dinner, hundreds of maggots start to fall from the ceiling. Ms. Tanner investigates the upper floor and finds that crates of spoiled food have caused the maggot infestation. Madame Blanc apologizes to the girls, and arranges for all of them to sleep in the practice hall. A wall of sheets separates the girls from the teachers, who are staying with the girls for the night. Suzy asks Sara if the teachers live in the school, but Sara tells her that they leave at 9:30 every night. When the girls sleep, a shadowy figure lays down on the other side of the sheet behind Suzy and Sara. The person has a very distinct, raspy, whistling snore and it frightens Sara, who wakes Suzy up. Sara tells her about a time last year when she had to sleep in a guest bedroom: late that night, she had heard the same snoring in the next room. Madame Blanc later told Sara that the school's directress stayed in that room, so the weird snoring means the directress is now here. This seems suspicious to Suzy and Sara, since all the girls have been told that the directress would not return to the school for weeks.
The next morning, Sara asks Ms. Tanner if the directress showed up last night, but Ms. Tanner denies it. As classes start, Madame Blanc's young nephew, Albert, is attacked by Daniel's guide dog. Enraged, Ms. Tanner interrupts class and tells Daniel never to bring the dog back or she'll have it put to sleep. Daniel yells at her and insists his dog would never harm anyone. Ms. Tanner throws Daniel's cane to the floor and tells him to get out, humiliating him as he fumbles around trying to find it. Daniel is enraged, and makes a veiled threat to Ms. Tanner: he is blind, but not deaf. Ms. Tanner is furious.
That night, after Suzy eats her meal Sara comes into her room and they listen while the teachers supposedly leave. However, Suzy notices that the footsteps are going away from the front door; therefore the teachers are not really leaving the school at all, but going someplace inside. Sara begins to wonder where they go, but Suzy becomes extremely drowsy and can hardly stay awake. Sara takes out a notebook and writes down the number of footsteps as the instructors walk by.
Daniel, who has been out at a bar, leaves with his dog. While in the middle of an empty piazza, his dog begins to bark at something. Daniel tries to calm down the dog, but he just gets more restless as they walk. Daniel begins to become frightened and stops, hearing strange sounds that indicate to him someone else is there. We can also see shadowy figures moving in the distance. As Daniel waits silently in the piazza, his dog suddenly attacks and kills him, tearing out his throat.
Suzy is troubled by the sudden number of deaths and approaches Madame Blanc. She tells Blanc that she heard Pat say something the night she died. Although Pat had said more, Suzy only heard "secret" and "irises". Madame Blanc says she will inform the police about Suzy's information, but Sara later gets angry that Suzy told this to Madame Blanc. Sara worries that Suzy's revelation has put the teachers on a hunt for whoever Pat was talking to that night, and that the teacher will obviously identify that person as herself. As the two go for a swim in the pool, Sara tells Suzy all about her friendship with Pat, and how Pat had been taking notes for months about strange occurrences at the school. However, when Sara is going to show them to Suzy that night, the notes are gone; now she knows that the evil forces in the school are onto her and her time is short. The only thing she has left is the list of footsteps she made. Sara tries to get Suzy to help her, but once again Suzy cannot stay awake. Sara begins to hear footsteps and flees Suzy's room just before an unseen person enters. Sara escapes to the attic, where she is attacked but hides in a room and latches the door shut. Her stalker tries to use a strait razor to unlatch the door. With nowhere else to go, Sara cowers away from the door when she notices a small window near the ceiling. Stacking several boxes on top of each other, she leaps through the window and into the next room; unfortunately, the small room is filled the brim with large, unruly bushels of razor wire. She tries to escape to an open door a few feet away but keeps getting tangled and cut. Just as she is near the door, the killer slices her throat.
The next morning, Suzy finds Sara's room empty. Ms. Tanner tells Suzy that Sara left early that morning without telling anyone. Suzy meets with a friend of Sara's, who turns out to be Sara's psychologist. He tells Suzy that Sara became troubled when a friend put the notion of witches in her head. Sara also found out that the school was founded by Helena Markos, a Greek émigré, who people thought was a witch. Markos was persecuted wherever she went, and she founded the school for the study of occult sciences and arts. However, Markos died in a fire, and the school was passed down to her favorite pupil who turned it from a school for the occult to a dance academy. Suzy talks to a colleague of Dr. Mandel who specializes in witches, Professor Milius. Milius explains to Suzy that witches are negative forces that change events only to do harm, and their goal is to gain personal wealth that can only be achieved by injury to others. He also tells her that a coven of witches can only do magic with the power of their queen. Otherwise, they are harmless.
Back at school, Suzy finds out that all the students are gone. She asks a servant, who tells her that all the students went to the theater, and that Ms. Tanner got the tickets. Suzy tries to call Frank Mandel, but a storm knocks out the phones. In her room, Suzy dumps her food out, and throws the wine down the sink, which looks suspiciously like blood. Afterwards, she is attacked by a vicious bat that flies in the bathroom window. She begins to hear the teachers footsteps, and remembers counting them with Sara. Following the count, Suzy traces their path and ends up in Madame Blanc's empty office, where the footsteps stopped. With only one door, she knows the teachers exited somehow. Glancing into a mirror, she notices irises painted on the wall in the elaborate grotto illustration that adorns Madame Blanc's office. Suddenly Suzy remembers what she had forgotten. When exiting the school, Pat said "The secret! I saw behind the door! Three irises! Turn the blue one!"
Suzy turns the blue iris and a hidden door pops open. She sneaks down a hallway and, hiding behind a curtain, she sees the entire coven meeting with Madame Blanc, who is sitting on a throne. She and the others discuss how they will kill Suzy. Conducting a black mass ritual, Madame Blanc partakes of some kind of communion wafer and says "Queen Helena, give me power!" Afraid they might find her, Suzy backs away and stumbles upon Sara's corpse. She flees into a connecting room, which turns out to be a bedroom. Asleep in the bed, obscured by sheer white curtains, is a shadowy figure, snoring loudly--the same weird snoring of the directress, whom Suzy now realizes is Helena Markos. Frightened, Suzy knocks over an ornamental statue which wakes up Helena Markos. In a horrible, raspy voice, Helena speaks to Suzy: "The American girl! I knew you'd come. You want to kill me!" Suzy picks up one of the sharp glass feathers from the statue and pulls back the curtain of the bed only to find it empty. Confused, Suzy looks around while Markos taunts her. A door slowly opens, and Sara's corpse, back to life and wielding a knife, approaches Suzy. As lightning strikes, Suzy notices a slight outline of Markos still sitting there on the bed; she is simply invisible. Suzy stabs her through the neck. Sara disappears, and the burnt features of Markos become visible as she dies; the weapon has penetrated through her entire neck, and she chokes to death. Things in the bedroom begin to explode, and Suzy rushes out. As she passes by their meeting room, she sees Madame Blanc, Miss Tanner, and the others, all collapsed and bleeding due to the death of Markos. Suzy runs away, and everywhere she goes, power exudes from her, destroying all in her path. Doors explode outwards before she can touch them, and walls crack and break as she passes. Finally she reaches the exit and walks out into the rain as the house burns behind her. Suzy smiles cryptically as she walks away from the school. Perhaps she is simply happy to have escaped, or perhaps it is as the legend goes, that whoever kills a witch inherits her power.