In June of 1941 a baffling Luftwaffe radio message is picked up by the decoders of Allied intelligence. It mentions a new invention with the codename Freya-the Viking goddess of love. Starting from this slender clue, intelligence analyst Hermia Mount begins to suspect the existence of a top secret experimental radar station on the coast of Denmark. Meanwhile Harald Olufsen, a brilliant young Danish student, is coming to the same conclusion by a different route. Although more interested in getting to know the alluring Karen Duchwitz, Harald is gradually drawn into Hermia's investigation. But when he finally learns the truth, he finds he has no way of getting to England with the information-except for a derelict Hornet Moth biplane rusting away in the nave of a ruined church...