Pursuing a ruthless enemy who wants to throw Europe back into the horrors of the Great War, Briers Allerdale returns to 1920s London to warn his masters in the Secret Intelligence Service of a dangerous anarchist plot. He will need back up - but of a very specialised kind. Borrowed from the cipher department Miles Siward moves into a 'couples only' boarding house, posing as Allerdale's 'wife'. Miles loves allowing his alter ego, Millie, to spread her wings but if Miles wants the other agent's respect he shouldn't betray how much he enjoys being Millie nor how attractive he finds Allerdale. Briers and Miles are helped and hindered by nosy landladies, Water Board officials, suave gentlemen representing foreign powers and their own increasing attraction to each other. Will they catch their quarry? Will they find love? Could they hope for both? The clock is ticking.