It is 1940 and the bombs are falling thick and fast on London. The royal family must do all they can to assure the British public of their solidarity. But what of the two young princesses - Elizabeth and Margaret? How can they be kept safe without jeopardizing morale in the capital?

Meanwhile Celia Nashe is delighted when she finally gets her long-awaited transfer to MI5. But whatever she was expecting of her mission for the war effort, it wasn't this. A crumbling castle in remote, rural Ireland, playing nursemaid to two pampered young girls.

But her posting soon turns out to be very far from tame. Questions are being asked by the locals about the identities of Celia's secret charges. And when a dead body turns up at the castle gates, it will take every effort to uncover the truth, and to stop it from coming to light.