LATE ON THE AFTERNOON OF MARCH 3, 1993, a young Hispanic man walked into the office of Madalax Real Estate, a run-down storefront in the heart of Little Colombia in Queens, New York. He asked to see the owner, Gladys Claudio, and was directed toward the back of the building. A few seconds later, there was the sound of gunfire: Guillermo Benitez-Zapata, a 21-year-old Colombian, had shot Claudio four times in the face. He returned calmly to the front of the office and, as he passed the desk of Claudio's terrified coworker, turned and pressed a finger to his lips. He made no attempt to conceal his face.

New to the detective squad of the NYPD's 110th Precinct, Billy Ahern had never been assigned a homicide case before. As baffling as it seemed that a Queens Realtor could be the victim of an execution-style killing, Ahern was determined to find those responsible—and would work for years with the Drug Enforcement Administration's "redrum" unit, which specializes in narcotics-related homicide, and as a member of the Queens Cold Case Squad. In the course of the investigation, he would make more than 40 arrests in the United States and would track down Benitez-Zapata. But the hit man had no idea who had sent down the order for the Queens killing. The search for the answer would span 14 years and three continents before entering its final act on an airstrip in the Amazon jungle in August 2008. By then, the investigation would have reached into the heart of one of the world's largest criminal organizations and brought down one of the wealthiest and most elusive drug kingpins to emerge from South America: Juan Carlos Ramírez-Abadía, known by the man who finally caught him as "the Colombian With a Thousand Faces" but more commonly as Chupeta—or "Lollipop."

PABLO ESCOBAR, THE MOST INFAMOUS OUTLAW in Colombian history, was finally cut down by police bullets on a Medellín rooftop more than 15 years ago. In the violent epoch that followed, dozens of other drug barons rose and fell, and the country was brought to the brink of anarchy. But none would reach the same reckless heights of notoriety that Escobar had. His gang of roughnecks was supplanted by the men of the Cali cartel, who preferred to be seen as respectable businessmen. They divided their enterprise into cells, to foil the work of law-enforcement agencies, separating distribution centers from "offices" of enforcement, transport, money laundering, and bribery. But for all its sophistication, the cartel remained committed to the use of horrifying brutality; after one DEA operation, suspected informers were immersed in barrels of acid. It was against this backdrop that Chupeta appeared.

Juan Carlos Ramírez-Abadía was born in 1963 in Palmira, Colombia, and grew up in a middle-class district of nearby Cali. Later, he told police, he earned an M.B.A. from the University of Miami. In his early twenties, he began to work in South Florida in what one law-enforcement source close to the case describes as "retail": selling cocaine from local labs a kilo at a time. At some point, he acquired the nickname Chupeta.