A mysterious crime in Peru revives a vampire legend that's more than 400 years old.

The first bottle—the one with the Inca Kola label still affixed—was filled with something thick and yellow-brown. The other bottle contained a dark fluid and some grainy bits. An evidence table had been carefully arranged for the cameras by the Peruvian National Police: The pair of one-liter soda bottles, a half-dozen small canisters, some coils of safety fuse, and a few sticks of dynamite—each labeled with display cards in block print. Gen. Eusebio Félix Murga, director of Peru's criminal investigations unit, balled his hand into a fist as he spoke to the gathered crowd. "We have broken up a criminal gang," he said, "which traffics human fat."

Three suspects were in custody; at least one had confessed. Police said the gang had been operating out of the highland jungle region of Huánuco, about 160 miles from Lima. There they would confront strangers on country roads and lure them into the jungle with the promise of employment. In a remote makeshift laboratory, a victim would be bludgeoned to death, his head and limbs hacked off with a machete, and his eviscerated torso hung from metal hooks. Votive candles warmed his abdominal flesh from below, so its rendered fat would drip through a funnel and collect in a basin on the floor. Reporters at the Nov. 19 press conference were shown a sketch of how all of this was supposed to work.

There was video footage, too. Twenty-nine-year-old Elmer Segundo Castillejos, who had been arrested a few weeks earlier at a bus station in Lima, was leading a column of police officers through a valley of coca plants. Gesturing with his cuffed hands, he points them to a trove of human remains—ribs, thigh bones, and the decomposing head of Abel Matos Aranda, who'd been murdered somewhere in the Andes in September.

Further details were hazy: Gen. Félix Murga reported that six members of the gang were still at large, including the ringleader—a man said to have been engaged in the practice since the 1980s. As many as 60 Peruvians, he surmised, might have been slaughtered for their fat. Castillejos and his buddies claimed to be getting $15,000 for each bottle of human grease, from a pair of Italian Mafiosi serving as intermediaries to the European cosmetics industry. According to the police, the material was being used for a line of skin-softeners.

The lead prosecutor in the case, Jorge Sanz Quiroz, referred to the suspects as brujos, or witches. But other officials used a more provocative nickname to describe those in custody—one that referred to an Indian legend that dates back more than 400 years, of pale-skinned vampires who kidnap peasants and suck out their fat with tubes and syringes. "It's an Andean myth that we've now been able to prove," announced a government spokesman. The police had captured a gang of pishtacos.

In a matter of days, the official story began to fall apart. Early reports challenged its central premise—that there might be any market at all for stolen blubber. What possible use could Westerners have for the flesh of Andean peasants? With obesity rates as high as 25 percent or 30 percent (PDF) in the developed world, weren't we already swimming in our own sea of fat?

Yes, a surgeon performing a facelift in Paris or New York might deposit a teaspoonful of fat along the creases at the sides of a patient's mouth. And it's true that some women now have fatty tissue injected directly into their bosoms, in a technique known, without irony, as "natural breast augmentation." For these procedures, though, doctors use the patient's own fat, cut from her belly or thighs.

Medical experts in Peru noted that liposuction clinics discard hundreds of liters of excess human fat every day. And even if the pishtacos did manage to fence their stolen grease, what about the body parts they left behind? The kidneys, livers, and lungs, for example—in-demand organs that would fetch a mint on the black market.

As reporters dug into the story, more details began to unravel. BBC Mundo reported that Interpol had no knowledge of the case, despite claims from the Peruvian police that a global manhunt for the two Mafiosi was in the works. On Nov. 30, the newspaper La República discovered that the local authorities in Huánuco, a region long known for its cocaine merchants and drug violence, hadn't been aware of any murder spree until the general gave his press conference.

The police were accusing the pishtaco gang of having hacked up 60 people in their jungle hut, but there was evidence for just one killing—the decapitation of Abel Matos Aranda. That murder now seemed more like the product of a local vendetta than some international conspiracy.