Prologue

The Doctor stood at the TARDIS console, still holding Susan's shoe, with Ian and Barbara looking on. Suddenly, he stood very erect, putting Susan's shoe down carefully and reached for a particular switch, and slammed it down hard. Susan had almost reached the TARDIS when its door closed in her face. She took the key from round her neck and tried to open it. Nothing happened.

"Grandfather," she screamed. "Grandfather!"

Suddenly she heard the Doctor's voice. 'Susan, please listen. I've safety-locked the door—you can't get in.'

Inside the TARDIS the Doctor could see Susan's puzzled face looking at him on the scanner. Gently he said, "During all the years I've been taking care of you, you in return have been taking care of me. You are still my grandchild and always will be. But now you're a woman too. I want you to belong somewhere, to have roots of your own. With David you will be able to find those roots and live normally like any woman should do. Believe me my dear, your future lies with David, not with a silly old buffer like me. One day, I shall come back. Yes, I shall come back. Until then, there must be no regrets, no tears, no anxieties. Just go forward in all your beliefs and prove to me that I am not mistaken in mine. Goodbye, Susan. Goodbye my dear."

And without hesitating, the Doctor pulled the dematerialisation lever, sending the TARDIS off into the Time Vortex, leaving his beloved granddaughter behind.

1, 268 years later (for the Doctor)...

'One day, I shall come back.' The thought echoed around the Doctor's head as he leant against the TARDIS's control console. That day had arrived.

Author Note: The majority of this chapter is an excerpt from the Target novel 'Doctor Who and the Dalek Invasion of Earth' by Terrance Dicks, published in 1977. This will only be a short story and will feel rather rushed. This is intentional, as I consider the story a filler for the Doctor's timeline while he takes time off from Hogwarts. Refer to the 7th chapter of 'Harry Potter and the Mystery of the Blue Box' for the full backstory.