This classic episode of Doctor Who, “The Dalek Invasion of Earth ,” featured (as the title indicates) the return of the Daleks. When Ian said he thought they had destroyed the Daleks on Skaro, the Doctor pointed out that that was at a different time, presumably in the future, while the Daleks clearly had spread elsewhere prior to that. This device would allow for enemies to return time and again. Having “defeated” the Daleks or the Cybermen or the Master on one occasion wouldn’t be decisive, not only because they might find a way to reappear, but also because it would as a rule be possible to encounter them at an “earlier” point from those enemies’ perspective.

Because at this stage in the history of the show, one simply saw a name for each part and not of an overarching story, the viewer didn’t know that the Daleks were on Earth until the very end of the first part. The episode did a great job of creating a sense of growing menace: a sign prohibiting the dumping of bodies in the river, a London that was in a state of decay and eerily silent, without even the chimes of Big Ben.

For a show with a limited budget, the episode does quite a good job of giving the impression that most of the action is taking place in a largely deserted London.

The story is quite compelling, and still enjoyable even for viewers today.

The most famous element, and one that it is interesting to reflect on in light of the show’s subsequent development of the time lord mythos, is that in this episode the Doctor says goodbye to his granddaughter Susan, who has fallen in love with a man who was part of the human resistance against the Daleks. This was the first time a major character, one of the Doctor’s regular companions since the first episode, departed from the show.

It is crucial to remember that at this point, we knew nothing of time lords, of different biology such as two hearts, of Gallifrey, or of regeneration. If Susan stayed behind, would she have children that were half time-lord? Would Susan regenerate, and if so, what would the result be for her relationship with David? Would she ever find a way back to Gallifrey, and if so, what would the consequences be? The Doctor says in this episode, echoing the very first episode of the first season, that one day he would return to Susan, just as one day they would return to their home time and civilization.

Although the Doctor would later say that he “borrowed” the TARDIS to go exploring, and to run away, there have been many hints that there is more to it than that. Presumably the fuller story will explain why he was on the run with his granddaughter but not the rest of his family (and some novels and fan fiction has tried to fill in some of this story in the past).

Perhaps the story of Susan will see some further exploration in the 50th anniversary special(s)? It seems only fitting that the Doctor would take River Song to meet Susan. And of course, let’s not forget that Susan makes an appearance in “The Five Doctors.”

If you are a fan of the show, what do you think happened to Susan, and what do you think the show might explore regarding her story in the future?