When Mara Cecova, the haughty and irritable lead of an avant-garde production of Verdi's Macbeth, is struck by a car outside the theater after a heated argument with the director and crew, her young understudy Betty steps into the spotlight. Given the prestigious role of Lady Macbeth, Betty initially feels a sense of dread but quickly becomes a sensation on stage.
On the highly anticipated opening night, an enigmatic opera fanatic watches Betty's performance from an empty box. When a meddling stagehand orders him to leave, the fanatic retaliates violently, murdering the stagehand by impaling him. Later, in her dressing room, Betty is celebrating with her boyfriend, Stefan, when the unseen assailant breaks into their apartment. After tying Betty to a pillar, he forces her to witness Stefan's brutal murder before escaping, leaving her traumatized.
Haunted by a horrific childhood memory of her own mother's murder at the hands of a similar hooded figure, Betty decides against going to the authorities. Instead, she confides in Marco, the director of Macbeth, fearing the killer might know her. The following day, Inspector Alan Santini arrives at the opera house to investigate Stefan's murder, while Betty avoids him, seeking counsel from her nurturing agent, Mira.
As rehearsals progress, a wardrobe seamstress named Giulia discovers that Betty's costume has been slashed. While trying to fix it, Giulia finds a mysterious gold bracelet sewn within the dress. The situation escalates when the killer appears once more, tying Betty up and attacking Giulia to seize the bracelet. In a struggle, Giulia is fatally wounded after uncovering the killer's identity. With Giulia barely alive, the killer brutally retrieves the bracelet, once again leaving Betty in a state of shock.
Seeking refuge back at her apartment, Betty encounters Inspector Santini and informs him about the incessant threat against her life. A detective is promised for her protection, but tensions rise when a man claiming to be Inspector Soavie shows up, leading to confusion over who can be trusted. As the situation unravels, Mira is tragically shot by the true killer as they attempt to force entry into Betty's apartment.
In an intense cat-and-mouse game, Betty narrowly escapes after finding the real Inspector Soavie fatally wounded. She hides in a ventilation shaft, fleeing to safety thanks to a brave local girl. Returning to the opera house, she learns from Marco about a plan to catch the killer and begins to confront her past.
As the next performance of Macbeth begins, chaos erupts when Marco unleashes a horde of aggressive ravens into the audience, attacking the murderer, who is revealed to be none other than Inspector Santini. A confrontation ensues, exposing Santini's dark past with Betty's mother and unveiling his twisted motive to replicate past horrors.
Blindfolded and tied up, Betty manages to escape Santini's fire trap and, along with Marco, escapes to the Swiss Alps to recover. However, when news breaks that Santini is still alive, a harrowing chase ensues through the wilderness. Marco sacrifices himself in a clash with Santini, allowing Betty to fight back using her wits. After a fatal confrontation, Santini is apprehended, and Betty finally finds solace in nature, symbolically freeing an ugly lizard as a mark of her liberation from the darkness that once consumed her.
