Documentary about how Tristan da Cunha, the most remote inhabited island in the world and a seven-day boat trip from Africa, could hold the key to unlocking one of the great mysteries of modern medicine - the genetic basis for asthma. Featuring Napoleanic garrisons, volcanic eruptions and ship-wrecks, the film uncovers the extraordinary history of Asthma Island, its unique people and the scientist who has spent his career trying to unravel the secrets of their past.