Rose; a name the Doctor would never forget for the rest of his days. The woman behind the name haunted him throughout time and space. Nothing he did and nowhere he had gone seemed to make any difference or dent. He had even met a new companion, Martha Jones, but their time together had been short lived because she could sense he would never be over his former companion and she didn't want to be a replacement for a ghost. So one day while he was sleeping, Martha had slipped out of the TARDIS quietly, leaving behind only a short note.

Doctor,

I'm sorry but I just can't stay and continue to be a replacement for your Rose. I know I'll never measure up to or ever be her as you so often remind me and yet I find myself falling for you with each passing day. I can't bear to stay and love you and know that there will never be any hope of any return feelings so I've decided to leave before I get my heart broken.

Yours forever,

Martha Jones

With that, she was gone.

If he was honest with himself, the Doctor would have said it was a good thing - Martha couldn't ever be Rose so why put himself through the hell of having someone around who wasn't her? It would have worked except he was afraid of being alone.

After Martha he decided to travel alone and try to cross the Void into which he had sent the Daleks and Cybermen to return home – home to the ruins of his dead planet.