The Dinansky Family have gone to spend their holiday in a caravan park in the seaside resort of Quinton. They have taken with them two old transmitter sets (walkie-talkies) from the Second World War which their grandfather has lent them.Walking along the beach, at some distance from one another, the two older children are talking to one another on the transmitters. Chaya trips and the dials shift frequency and she hears from the machine a man's voice, a voice full of terror. "Please, please help! If anyone can hear me, please help".Immediately they are all plunged into a breathtaking and dangerous adventure.This book was originally published in serial form in the Concord Magazine, London, England