Three centuries ago, the witch Mad Dolly is captured on the orders of Lord Garrick. She is to be burned at the stake, but she summons the Devil, sparking flames that leap from an executioner. A disembodied arm bursts through a wall to strangle Lord Garrick as he hurries back to his house. The curse lingers on the family when the sword-wielding Mad Dolly beheads Lady Garrick, Mary Maude dooming the Garrick line.
As the credits roll, we learn this sequence is the ending of a horror film directed by James Garrick John Nolan, the last of the Garrick line, who now owns the old Garrick house and hosts a private preview for his cousin Ann Carolyn Courage, an aspiring actress. James believes the story is true and has even inherited Mad Dolly’s sword, setting a tense stage for what looks like a night of cinema and superstition.
Gary, a mesmerist Michael Craze, takes center stage at the party and hypnotizes Ann as a trick. In the trance, Ann seizes the sword and makes a half-jest at James, wounding him slightly. The guests overwhelm her, and she comes to, leaving the house in a shaken rush. Later, Carol Tucker Glynis Barber departs the gathering only to be stabbed to death in the surrounding woods by an unseen assailant. Ann returns to her hostel in London with bloodstained hands, watched over by her roommate Suzy Sarah Keller.
On a lonely country road, Suzy’s car breaks down and she heads to a nearby house to seek help, dialing a tow service when no one is home. Waiting for assistance, she encounters a tall, shadowy figure that seems to stalk her at every turn, only to discover that the menace is the garage mechanic she phoned for—a creeping tension that blurs the line between fear and reality.
The terror escalates with more grisly deaths. At the strip club where Ann and her friends work, a patron who gropes Ann is ejected by a bouncer and later meets a brutal fate on a row of spikes. At James’s film studio, an overhead lamp crashes down and kills Les, a short-tempered director trying to shoot a risqué movie called Bathtime with Brenda. Viv—the title character and one of Ann’s friends—is stabbed to death at the hostel, heightening the sense that the past is bleeding into the present.
Ann visits James’s assistant Philip James Aubrey at the studio and confesses she has no memory of the attack on James or how she got home the night Carol was murdered. After she leaves, props and equipment start flying around the studio and pelt Philip, who is then decapitated by a falling sheet of glass.
As the investigation unfolds, Ann slips away from a questioning Suzy as police circle around Viv’s death. An officer pursues her but is repeatedly crushed by his own car, driven by an unseen force that seems to be bending the world to a darker pattern. En route to the Garrick house, powerful winds lift a parked car into the air, forcing Ann to jump free to safety.
Inside the house, she experiences vivid visions and watches objects move of their own accord. An unseen figure suddenly appears, and she swings an axe, only to discover she has killed James Garrick. The room fills with the cackling echo of Mad Dolly’s spirit as her sword skims the air and fatally impales Ann against a wall, sealing the supernatural horror that has haunted the Garrick family.
