Dr Adams and his pilot Peters are flying to Madagascar to save the ailing statesman General N'Mobo when their atomic-powered jet develops a malfunction. The plane crash-lands in the Kenya savannah, and whilst Adams and Peters survive their ordeal, their canisters of the life-saving heart stimulant Rexsta Seven are damaged. The two men are taken prisoner by Masai tribesmen, while the Rexsta Seven leaks into the landscape. As General N'Mobo's condition worsens, Jeff Tracy orders a search-and-rescue operation for Adams and Peters. The Thunderbirds' mission is complicated by strange behavior of the local wildlife, now contaminated by Rexsta Seven...