Book excerpt: Guillermo Macias disappeared in 1976, in Argentina's 'Dirty War'. Twenty years later, in 1996, his terminally-ill father was determined that someone should find out what had happened to him and why. He had the names of two men he wanted questioned one in Mexico City, the other in a prison on the Colombian island of Providencia but no one to ask the questions. A friend of the family suggested retired SAS hero Jamie Docherty, now living with his Argentine wife in neighbouring Chile. Marysa Salcedo had disappeared on a picnic the previous year, along with four other young women. Her family had given her up for dead when her older sister Carmen stumbled upon a Miami newspaper story that mentioned two of the friends. One had just died of a drug overdose; the other, half-deranged, told a garbled story of sexual slavery on a Caribbean island which sounded suspiciously like Providencia. MI6 and the British Government were also more than a little interested in the island. They were certain that a huge drug-trafficking empire was run from the prison, and knew that at least some of the profits were being funnelled by its Argentine 'guest' into the financing of a mercenary invasion of the Falklands. Ignored by the Colombian authorities and mysteriously obstructed by their American allies, the British had no choice but to send their own elite force the SAS.