Clara climbs into Rusty’s memory banks and begins activating memories as she crawls through it. In an interesting moment that could either be a nod to fans or a crucial hint, the very first memory she reactivates is a shot taken straight from the much earlier "Dalek" episode when one of the Daleks kills a soldier. Eventually she activates the memory of the star being born, which allows the Doctor to mind meld with Rusty in order to convince it that it does have a moral compass. Capaldi’s performance in this scene should convince anyone that he is the Doctor, as he delivers a hauntingly captivating speech to sell the beauty of the universe.
But in a rare moment, the Doctor’s plan backfires as the Dalek does not see the wonder behind the universe that the Doctor does but instead the utter hatred that the Doctor has for the Daleks. This pure hatred override Rusty’s own programming and turns Rusty against his own kind. Rusty does not seek to exterminate everything but Daleks anymore—now it seeks to exterminate only other Daleks. His turn winds up saving the day as he destroys the Dalek invasion force and puts out a retreat signal after falsely indicating that the human ship has activated its self-destruct. The Doctor, though, sees this as a failure because "Victory would have been a good Dalek." Instead he showed it a hatred so fierce and deep that it overrode even the Daleks own hatred. In other words, the Doctor turned a monster into another kind of monster. In a line that closely mirrors one from "Dalek," the Dalek tells the Doctor that he "is a good Dalek" and then leaves to hunt down other Daleks. The Doctor, shaken from what he was just told, brusquely says goodbye to the soldiers and leaves with Clara. Blue asks to join but the Doctor turns her down saying that it was too bad that she is a soldier.
Back in the present day London, Clara tells the Doctor that she doesn’t have an answer to his earlier question of if he’s a good person. But he tries, and that might just be the point. She meets with Danny back at the school, where he makes certain that she does, indeed, want to go out with him because he feared she might have a rule against soldiers. "No," she says, "not me."