According to the autopsy report, Barrie Mayer died of a heart attack while standing in line at London's Heathrow airport. The fact that Barrie was young and in superb health was enough to raise suspicions in her best friend Collette Cahill's mind. But the added fact that Barrie was also a part-time courier for the CIA and held a less-than-professional attitude towards her little "side-line" profession pushed Cahill over the edge from suspicion to downright fear.