During World War II, British spy Livy Nash lost one of her only friends, fellow agent Margot Dupont, who disappeared during one of their missions. In this sequel to Spitfire, however, the British pick up Margot's call sign—"Nightshade"—years after the war, and Livy can't help hoping, even as she wonders if it's a trick. Despite her unease, Livy sets out to find Margot, aided by her boss, the charming Ian Fleming. When evidence arises that a handsome Russian spy might have information about Margot, Livy agrees to her most dangerous mission yet: going undercover as a double agent to spy on the infamous "Red Devil."