Frankie is in her forties, ambitious and successful. She works in the aerospace industry at Filton, designing surveillance drones for the military. She never married, and is completely in control of every part of her life. Her closest relationship is with her father, who worked as an engineer on Concorde. But her life changes forever when she embarks on a passionate affair with Kahil, a French/Algerian aerospace student, twenty years younger than her. One day, she arrives at work and is detained by the security services: Kahil is a person of interest to MI5. Her well-ordered life starts to unravel in a welter of suspicion and prejudice, as Frankie no longer knows whether to follow her passion or listen to the doubts that increasingly overwhelm her.