It is 1941, and England is at its lowest ebb, undernourished, underinformed and terrified of imminent invasion. Even at Eden Park, the lovely country estate where Poppy, Kate, Lily, Marjorie and her adopted brother Billy have all become part of the rich tapestry that is being woven around them, confidence is at an all-time low. And that is before the authorities discover there is a double agent operating within the M15 unit based there.