With the Doctor missing for months, it's up to Graham, Ryan and Yaz to investigate footage of a prototype security drone that looks suspiciously like a Dalek. The robots are the work of their old foe, businessman Jack Robertson, who has allied himself with Jo Patterson, an unscrupulous politician with her eyes on Downing Street. But even Robertson is unaware of the scale of the Dalek scheme unfolding within his own facilities. And, when the Doctor is rescued from prison by Captain Jack Harkness, she may be forced to resort to a solution that's worse than the problem itself.