The Broken Doctor: Part One
Before the World Broke
With all of his remaining strength, the Master sent Rassilon and Gallifrey back through the Time Lock. Unable to push the Doctor away when he cradled him, the Master attemped to regenerate, but it was no use. His life was over. The Doctor, in a fit from witnessing the second end to his planet, attempted to merge with the Master. It shattered their minds instead, leaving the Doctor with half of his memories, a distinct lack of compassion and guilt, and the Master's drums. Afterwards, the Master supposedly died in the Doctor's arms. Overcome by the drums, the Doctor left the Master's body behind, left Wil behind, and went out to live the rest of his life the best he could.
He took on Luke Campbell as his Companion for a year, trying to regain his lost memories and sense of self. He ignored the call of the planet Earth during the 456 invasion, running far, far away from a world he both loved and hated. Jack Harkness allowed 12% of the children of every country to be taken to satisfy the 456, allowing his Ianto and his grandson to survive. Perhaps it was because of this that the world broke apart. Or maybe it was simply the fate of this universe. Many Doctors have their theories. None have the answer or the ability to stop the merging of realities.
Return to Earth
Deciding it was time to let Luke go in order to save his life from a future he had forseen for the boy, the Doctor decided to get reaquainted with Earth once more. He met Rose Tyler and, despite knowing that she could not possibly be the one he left on the beach in Pete's World, attempted to regain her friendship through a mutual love of banana splits. She was the first to realize something was wrong with him, and with this world she had inadvertantly crashed into trying to find her own Doctor.
Very soon after, the Doctor met Theta Sigma, a metacrisis with a much darker, much more sordid past. Drawn to him immediately because he cooled the drums that pounded in his head, the two began a very, very weird friendship.
Sometime later, the Master and the Doctor were reunited. Somehow, the Master managed to survive. Perhaps it was because of the merge? This is a question that has never been answered. As expected, the Master wanted nothing to do with the Doctor, but the Doctor refused to let him go again.
As the friendship with Theta progressed, the Doctor was brought to meet the Red TARDIS and not long after, was given a room there to stay when he wished. The first inkling of the Valeyard began to show up very soon after when the Doctor killed a fruit vendor for trying to sell him a pear. There was another incident at an Alien Marketplace where the Doctor beat a boy that bumped into him. Theta finished the job to save the Doctor from committing murder.
Broken Jack bit the Doctor after giving him a kiss. Thus, the Doctor's obsession with kissing began.
Death of the Doctors
Broken Jack, in a fit perhaps because of his obsession with Alec (a Doctor look alike) or even because his anger at the Broken Doctor, began to kill Doctors. At one point, he gave the Master a left over TARDIS. During this time, the Doctor met Pancake Rose and began a rather innocent tryst with her based on his new found love of kissing, and about Theta's enjoyment of engaging in sex with men, which seemed strange to the Doctor.
For whatever reason, the Doctor began to wear very odd clothing, all sorts of different colored t-shirts and trainers in bright, bold colors. He would later discover that the frequency to keep the drums at bay when Theta was not with him was to wear shades or yellow, green, and purple.
After a bad night, another Doctor left dead by Jack, the Doctor confronts Theta in the Red TARDIS. He learned that Theta was immortal -- having just been shot after sex with his Jack -- and impulsively kissed him, only to get the spent bullet in his mouth. After hundreds of years of lack of intimacy, Theta coerced the Doctor into his bed and they became lovers.
Finally, in order to stop Broken Jack, Theta posed as Alec and he and the Broken Doctor locked up Jack in the Red TARDIS. Thus, the deaths of the Doctors was ended. The very next morning, the Doctor went on a date with Pancake Rose, hardly realizing it was a date. The Doctor flipped out when it becomes too intimate. Disraught and unnerved, the Doctor spent some quality time with the Master and got a kiss in the name of science! This was exactly what the Doctor needed, a kiss to calm him.
Part Two will continue with the Raid on the Red TARDIS!