Rue Armengaud was a quiet Paris street lined with one- and two-story private residences, each with its sloping guttered roof. Towering above its neighbors was Number 26, an eight-story modern structure of glass, steel and stone, the headquarters of Interpol, the clearinghouse for information in international criminal activities.

Detective Max Hornung was talking to a computer in the huge, air-conditioned basement room when one of the staff members walked in and said, "They're running a snuff film upstairs. Want to see it?"

Max looked up and said, "I don't know. What is a snuff film?"

"Come take a look."

Two dozen men and women were seated in the large screening room on the third floor of the building. There were members of the Interpol staff, police inspectors from the Surete, plainclothes detectives and a scattering of uniformed policemen.

Standing at the front of the room next to a blank screen, Rene Almedin, an assistant to the secretary of Interpol, was speaking. Max entered and found a seat in the back row.

Rene Almedin was saying, "...for the last several years we have been hearing increasing rumors of snuff films, pornographic films in which at the end of the sexual act the victim is murdered on camera. There has never been proof that such films actually existed. The reason, of course, is obvious. These films would not have been made for the public. They would have been made to be shown privately to wealthy individuals who got their pleasure in twisted, sadistic ways." Rene Almedin carefully removed his glasses. "As I have said, everything has been rumor and speculation. That has now changed, however. In a moment you are going to see footage from an actual snuff film." There was an expectant stir from the audience. "Two days ago, a male pedestrian carrying an attache case was struck down in a hit-and-run accident in Passy. The man died on the way to the hospital. He is still unidentified. The Surete found this reel of film in his attache case and turned it over to the laboratory, where it was developed." He gave a signal and the lights began to dim. The film began.

The blond girl could not have been more than eighteen. There was something unreal about watching that young face and budding woman's body performing fellatio, analingus and a variety of other sexual acts with the large hairless man in bed with her. The camera moved in to a close-up to show his enormous penis driving into her body, then pulled back to show her face. Max Hornung had never seen her face before. But he had seen something else that was familiar. His eyes were fixed on the ribbon that the girl was wearing around her neck. It triggered a memory. A red ribbon. Where? Slowly, the girl on the screen began to build to a peak, and as she started to climax, the man's fingers went around her throat and began to squeeze. The look on the girl's face changed from ecstasy to horror. She fought wildly to escape, but his hands pressed tighter, until at the final moment of orgasm the girl died. The camera moved in for a close-up of her face. The film ended. The lights suddenly came on in the room. Max remembered.

The girl who had been fished out of the river in Zurich.

At Interpol headquarters in Paris, replies from urgent inquiry cables were beginning to arrive from all over Europe. Six similar murders had taken place - in Zurich, London, Rome, Portugal, Hamburg and Paris.

Rene Almedin said to Max, "The descriptions match exactly. The victims were all blond, female, young; they were strangled during sexual intercourse and their bodies were nude except for a red ribbon around their necks. We're dealing with a mass murderer. Someone who has a passport, and is either affluent enough to travel extensively on his own or is on an expense account."

A man in plain clothes walked into the office and said, "We ran into some good luck. The raw stock of the film is manufactured by a small outfit in Brussels. This particular batch had a color-balance problem, which makes it easy for them to identify. We're getting a list of the customers they sold it to."

Max said, "I would like to see that list when you have it."

"Of course," Rene Almedin said. He studied the little detective. Max Hornung looked like no detective he had ever seen. And yet it was Max Hornung who had tied the snuff murders together.

"We owe you a debt of gratitude," Almedin said.

Max Hornung looked at him and blinked. "What for?" he asked.