Four Flies on Grey Velvet

Roberto Tobias, a drummer in a rock band, becomes the target of a stalker who follows him for days wearing dark sunglasses. The watcher remains unseen and pervasive, creating a constant sense of danger. Roberto tries to carry on with his life while the threat looms.

One night, the stalker confronts Roberto in an empty opera house. The stranger pulls a knife and a brutal struggle follows, during which Roberto accidentally stabs the man with his own knife. The stalker collapses, seemingly dead.

A masked figure on a balcony snaps several photographs of the confrontation, capturing the moment of violence. The images deepen the mystery and imply that the attacker is orchestrating the events. The killer remains an unseen presence.

In the days after, Roberto receives threatening letters, photographs, and the dead man's identity card naming Carlo Marosi. He is also haunted by a recurring nightmare in which he is beheaded in a Saudi square, which he believes is a premonition. The clues link the stalking to a larger conspiracy.

That night, the masked tormentor ambushes Roberto at his home and knocks him unconscious. The intruder warns they are not finished with him, leaving a chilling sense of danger in the house.

After regaining consciousness, Roberto confesses everything to his wife Nina, fearing arrest. Their live-in maid Amelia overhears the confession, recognizing an opportunity to leverage the situation.

Amelia tries to blackmail the couple and arranges a meeting with the tormentor in a park. The unseen assailant kills Amelia during the meeting, cutting off her ability to use the leverage.

Nina's cousin Dalia arrives to stay with the couple, bringing a new dynamic to the household as the mystery deepens.

It is revealed that Carlo Marosi is alive and had conspired with Roberto's tormentor to fake his own death using a prop knife. As the plan spirals out of control, Marosi tries to back out, but the unseen mastermind kills him.

Roberto hires Gianni Arrosio, a flamboyant private investigator, after a tip from Godfrey the beatnik artist. Arrosio begins following leads and digging into the case.

Arrosio visits Villa Rapidi and speaks with a doctor about an unnamed patient diagnosed as a homicidal maniac. The patient's father dies and the patient is discharged, hinting at a troubling backstory connected to the case.

Trailing the unnamed patient in a subway, Arrosio is ambushed and murdered with a poison-filled syringe in a bathroom stall. His death removes one of Roberto’s key links to the truth.

Dalia begins to suspect the killer's identity, but the killer appears and stabs her to death while she is alone in Roberto's house. The crime heightens fear and leaves Roberto increasingly isolated.

The police use optography to reconstruct the last image Dalia saw before dying, which yields four dark smudges resembling flies. The clue links the mystery to a recurring fly motif and to the killer’s identity.

Godfrey advises Roberto to wait with a gun in the house. The pendant Nina wears, a fly in glass, swings as a macabre clue. Roberto realizes Nina is the killer; she shoots him in the shoulder. Godfrey arrives to distract Nina, who then flees in Roberto’s car, which crashes into a truck and explodes, decapitating her.