Westmorland, 1949. Someone is mutilating livestock on the fells. Who would do such a horrible thing? Ruth Tyler, a police sergeant based in Ambleside, needs to speak to the fly camper in a hidden valley… London, 1938. For Jack Rambler, a boyhood of coded messages, daring expeditions, and the art of disappearing was child’s play. Now these very skills unexpectedly propel him into the clandestine world of espionage and his first mission: to infiltrate an occult society with links to Nazi Germany… France, 1943. On a secret airfield near Belfort, an SOE radio operator waits to meet her new handler, an agent flying in from RAF Tempsford with instructions to trust nobody… His codename is Hirondelle.