It's a story that has become tragically familiar: travellers, often young and healthy, visit sun splashed tourist destinations, fall ill and suddenly die. In the sudden deaths of Canadians Noémi and Audrey Bélanger, Thai authorities are quick to speculate on what might have happened, including drugs and food poisoning. There are even suspicions about a toxic cocktail laced with a chemical used in mosquito repellant. But Mark Kelley learns the Bélanger sisters are just the latest victims in a string of unexplained tourist deaths in the area, and examines a new theory — fatal exposure to toxic pesticide sprays used in hotels to control bedbugs. Linden MacIntyre consults pathologists, toxicologists and other specialists about what might have killed the two best friends. Meanwhile, their families press authorities to try to get a final answer in a country where bad news about the death of tourists is never welcome.