Britain is at war, and a secret arm of the British government called the Ministry of Unladylike Activity is training up spies. Enter May Wong: courageous, smart, stubborn – and desperate to do whatever she can to help end the war, so she can go home to Hong Kong. May knows that there is no one more perfect to become a spy than a child. A child can go places, see things and listen in on conversations in a way that no adult ever can. When May and her friend, Eric, are turned away by the Ministry, they take matters into their own hands. Masquerading as evacuees, May and Eric arrive at Elysium Hall. It soon becomes clear that one of the family is passing information to Germany. May and Eric know if they can gather enough evidence on their suspect, the Ministry will have to take them on. But there are more secrets at the Hall than May or Eric could ever have imagined. Then, someone is murdered!