Coronation Day, 1953. In a Somerset village, Molly Heywood slips away from the celebrations to her friend's cottage and makes a shocking discovery: Cassie is dead and her six-year-old daughter Petal has vanished. In her grief, Molly seeks help from her friend George, the village policeman, but no one can find Petal. The only clue is a letter from London, where Cassie once lived. Molly resolves to go to London, but is she risking her life?