"Into the Dalek" is the second episode of the eighth season of Doctor Who, and was first broadcast in August of 2014. It was written by Phil Ford and Steven Moffat, and starred Peter Capaldi as the Twelfth Doctor and Jenna Louise-Coleman as companion Clara Oswald. It also featured Samuel Anderson as new companion Danny Pink, who is here shown in a subplot but who is not yet traveling with The Doctor.
The Doctor rescues a young woman who is fleeing from a Dalek ship, and when he returns her to her base, he is ordered killed: until they find out that he is a doctor, and might be able to help a patient they have. That patient is another Dalek, one that has gotten "sick" and hates other Daleks. After retrieving Clara, he and some soldiers are miniaturized (in a homage to Fantastic Voyage) and injected into the Dalek, where they must figure out the mystery of what makes a Dalek turn "good".
The episode did a good job in both defining the character of the new Doctor, and the new timbre of the show. Capaldi's Doctor is much more sardonic, to the point of being callous, compared to recent Doctors. The show also addressed military issues, with the theme of Doctor as soldier versus Doctor as healer once again brought up. Whether this will be a consistent theme for this season remains to be seen.
Another point of interest for me is how often Revival Doctor Who has used The Daleks both as enemies and as philosophical foils for the Doctor. Before I started watching classic Doctor Who, I thought that this was something that the new series had inherited from the old. While it is true that the Daleks were introduced very early in Doctor Who, in the second story, and were used quite a bit during the First Doctor's run, they were not actually that widely used during much of the program's most popular years. For example, in the 66 stories of the Third and Fourth Doctor's run, between 1970 and 1981, only five had The Doctor fighting the Daleks. In this episode, the Doctor explicitly states that his contact with the Daleks gave him his self-image as a person who fights for good, and yet the entire concept of the Doctor as being the existential enemy of the Daleks seems to be an invention of the Revival Who.