A former patient of famed plastic surgeon Helmut Berger as Dr. Flamand seeks revenge after a botched operation, throwing acid at him but missing; the acid instead lands on his sister Ingrid Flamand, leaving her severely disfigured and drawing Flamand into a darker obsession with cosmetic “miracle” cures. In Paris, during a photoshoot, Brigitte Lahaie as Nathalie orchestrates the kidnapping of Barbara Hallen, who is portrayed by Caroline Munro, and hauls her to the basement of Flamand's clinic. There, it becomes clear that Flamand abducts young women and uses their blood and body parts to perform his notorious, pseudo-medical treatments for his patients, a gruesome routine that shadows the city’s glamour.
In New York City, Barbara's father, Terry Hallen, hires her ex-boyfriend, private detective Sam Morgan (Christopher Mitchum), to locate her. Once Morgan arrives in Paris, he begins a careful and perilous investigation. Flamand, ambitious to graft Barbara's face onto his own daughters, collaborates with Nathalie while being advised by surgeon Dr. Orloff to seek help from Dr. Karl Heinz Moser, who agrees to assist. The team returns to discover that Barbara’s face has already been badly cut by Flamand's mute assistant Gordon, setting off a radiating tension that threads through the clinic’s halls.
As Morgan presses on, Flamand abducts another girl, Melissa—a call-girl and former patient—to use for the transplant. Anton Diffring arrives as Dr. Karl Heinz Moser to aid the operation. During the procedure, Melissa’s face is sabotaged, and Gordon retaliates by severing Melissa’s head with a chainsaw, prompting Flamand and Nathalie to seize another woman to continue their dangerous plan. Morgan traces a credit card belonging to Barbara to the Paris suburb of Saint-Cloud and then to Flamand’s clinic, where security footage confirms Nathalie’s watch matches Barbara’s.
Returning to the clinic, Morgan finds the basement, where a nurse who had entered earlier is killed by Gordon. The trio—Flamand, Moser, and Nathalie—ultimately remove Barbara’s face and graft it onto Ingrid’s skin, a shocking switch that shifts the balance of power inside Flamand’s operation. Morgan confronts Gordon and kills him, but he can only reach Barbara and the other captives before he’s trapped in Barbara’s cell by Nathalie. Flamand, Moser, and Nathalie brick up the cell, leaving Barbara and Morgan alive but imprisoned as authorities close in. In the tense final moments, Flamand, Nathalie, and Ingrid prepare to flee France on Moser’s advice, while Barbara and Morgan survive in their cells. Sam reveals he has sent Terry a message, and that if no reply comes within 12 hours, Terry should “send in the marines, Merry Christmas.” Terry responds by ordering his office to secure the first flight to Paris, hoping to rescue the two before it’s too late.
> "send in the marines, Merry Christmas."
