One of the biggest mysteries left unsolved since the beginning of the Doctor Who relaunch in 2005 is what happened to the Doctor’s granddaughter, Susan Foreman.
When last we saw, her fate was left in the air:
Susan continues to travel with the Doctor and her two teachers until the 1964 serial, The Dalek Invasion of Earth. During the events of that story, Susan falls in love with David Campbell, a young freedom fighter in the 22nd century. However, Susan feels that she has to stay with and take care of her grandfather. The Doctor, realizing that Susan is now a grown woman and deserves a future away from him, locks her out of the TARDIS and leaves after a tearful farewell. Carole Ann Ford had expressed a desire to leave the series as she felt the character of Susan was too limiting. Ford reprised the role of Susan on television in the 20th anniversary special The Five Doctors (1983), but no mention of David, or what became of him, was made.
Later hints are dropped that she, like all the other Time Lords and Time Ladies, died during the Time War. But then something curious happened.
In Part 2 of The End of Time, an unnamed Time Lady appears standing next to Rassilon. There has been much speculation as to who this woman is and Russel Davies has been purposefully vague, saying, “I like leaving it open, because then you can imagine what you want.” This is supremely unhelpful. But that’s never stopped us before.
This unnamed Time lady and the Doctor share a meaningful look of recognition during this scene. This look is pretty much the basis for a lot fo fan speculation as to the woman’s identity.
Here’s my theory as to who she is: Susan Foreman, The Doctor’s Daughter.*
At some point in the future, The Doctor and River Song have a daughter. Due to the unique nature of River Song’s biology, this daughter inherits the Time Lord ability to regenerate. It is later discovered that their daughter will play an important role on the outcome of the Time War.
In order to safeguard her from this fate, The Doctor decides to hide his daughter in the one place no one would think to look for her: with himself. After she regenerates into the form we know of as Susan, Foreman, River deposits her with the First Doctor, informing him that she is his granddaughter. He raises her as such, never realizing otherwise.
Later, after Susan looses David to the Dalek’s in the 21st century, she decides to embrace her Time Lady heritage and goes traveling. Due to a run in with Captain Jack in the 52nd Century (before he becomes immortal) She finds a back door into the Time War and fulfills her destiny by becoming part of it. She helped the Doctor fight the Time war, and helped him escape, and as punishment, was forced to stand beside Rassilon and watch as he attempted to kill her father, only to be thwarted by the Master.
I like this theory,not only because it’s mine, but because it has some nice timey-wimey stuff going on, plays with continuity, and opens up some opportunities for fun story telling and character development. Everything that is great about the Doctor, when done right.
* No, not Jenny, the chromosome-swapped clone of the Doctor from The Doctor’s Daughter. That episode was, frankly, confusing and kinda crap, so we’re just going to pretend it didn’t happen, just like the writers.