A nuclear scientist boards a miniature railway en-route to a nuclear power station. He is carrying top-secret plans for a nuclear processing plant to be built to store all the country's nuclear waste in a vast underground bunker at Downsend. This would, of course, involve a lot of disruption and upheaval for those already using the marsh. When the train arrives at Downsend the professor is missing. Not everyone is happy with the government's plans...