A United Nations investigator crosses paths with a pair of psychic sisters on his way to Trollenberg observatory in the Swiss Alps, which has been plagued by a series of mountaineer disappearances that may be related to a radioactive cloud at the mountain's south face.
A wristwatch-smuggling gang bring watches into the country in a car's petrol tank. Poor Zena Marshall knows too much, so the gangs abducts her. Stalwart customs official Anthony Steel struggles manfully to rescue the girl.
The work of Peter Ketley on Fisheries Research in Devon is being disorganised by a mysterious new method of salmon poaching. His young brother Bob, with the help of two children from London, eventually uncovers and catches the poachers.
