When a Judoon platoon invades Gloucester, the Doctor races to identify the fugitive for whom they're hunting. Her investigation leads her to a tour guide named Ruth Clayton, who is unaware that her husband, Lee, is hiding a murky past. But when Ruth begans experiencing strange flashbacks to her childhood, the Doctor begins to suspect that there may be more to the Judoon mission than meets the eye. Meanwhile, Graham, Ryan and Yaz find themselves inadvertently teleported away from Earth by an old ally of the Doctor's, who bears a warning from the future.