The Doctor-who has briefly left Clara behind as she teaches at Coal Hill School-rescues a soldier from a Dalek fleet in the future. Eventually, he’s brought aboard her spaceship, where he discovers an interesting conundrum-a captured Dalek, but one that seems to believe that all other Daleks are evil. The Doctor agrees to try to figure out what’s “wrong” with the Dalek.
Meanwhile, back in the present day, Clara flirts with fellow teacher and veteran, Danny Pink, and the two agree to date.
The Doctor then picks up Clara and tells her about the situation. Since his regeneration, he’s been wandering about his new persona-is he a good man? Clara is not sure either.
Shrunk and placed inside the Dalek in the future, the Doctor, Clara, and a group of soldiers try to find out what’s up with this “good” Dalek. However, the Dalek’s tank-like body has it’s own interior defenses, such as nasty antibodies:
Eventually, the Doctor discovers that the Dalek-which he nicknames “Rusty”-has developed a sense of goodness after witnessing the birth of a star, but also seems to be suffering from a radiation leak.
The Doctor repairs the link, but unfortunately it reverts Rusty to the old Dalek way of thinking. He also sends out a distress call to his “brothers”, which then board the ship and start attacking.
Eventually the Doctor re-links with Rusty, showing him the view of the star being born again, and also telepathically communicating his own utter hatred of the Daleks; causing Rusty to turn to the side of good again (but also disappointing the Doctor’s sense of morality). Rusty turns against the Daleks, and joins the human cause, but the Doctor is still morally somewhat unsure of himself, with even Rusty saying that he would make a good Dalek (While Rusty himself is a “bad” one). However, Clara feels the Doctor is well-intentioned, even though he’s still not sure of his new self.