A military plane ditches into the sea whilst carrying three nuclear weapons on board. While the RAF mounts a search mission, an unidentified object is washed up on the shore near Byfield pier on the south coast of England. It is found by two men, Geoff Harker and Sam Billings, who decide that it must be a weather detecting device, and so begin to strip it down for parts. Toby is sent to investigate the device, but he soon finds himself faced with the terrifying prospect of disarming a very live bomb.