Disclaimer: Doctor Who, Donna, Rose...etc., etc., etc., don't belong to me. Of course, even after all this time, I STILL wish David Tennant belonged to me, but he doesn't, he belongs to himself. Be that as it may, no infringement of copyright intended. This is fun, not a money making venture.

Cause and Effect

Chapter One

It was a wrench to pull himself away from the Earth, but the Doctor knew that it had to be done. The indifference of Donna's farewell – such as it had been – had left him more miserable than he had been aware he would feel.

It had to be done, he reminded himself. She is a wonderful person and the human race will benefit much more from her being alive than from her pointless death.

The thoughts brought him no comfort at all as he stood at the TARDIS console which only an hour or two ago had been packed to the gunwales with bodies and was now so very, very empty.

Situation, he thought grimly, normal.

It had been a bizarre few hours, one way or the other and even the Doctor, so used to peculiar happenings and strange events had felt the emotional shockwaves more keenly than he could have imagined. Coolly, clinically, he took each one and dealt with it in turn. The aversion of the end of reality at the hands of Davros and his Daleks was a long, long way down the list. That was almost run-of-the-mill in comparison to the rage of emotions that flowed through his tired body.

He had been reunited with Rose, only to then be separated from her again, most likely forever. But when he put it into perspective, that was well and good. It had served an important purpose, which had been to demonstrate to him the surprising realisation that was, in fact, over her.

Not forever, of course, and certainly not completely – but he definitely moved on. No, he would never be completely over Rose – but the other 'him' was a different kettle of worms. Or can of fish. Or some other bizarre human metaphor involving animals and receptacles. After all, the other 'him' had been force-grown from the hand of a Time Lord who had not been changed by the intervention of Rose, Martha and Donna's humanity. He represented all that the Tenth Doctor had been in his early days – impulsive, emotion-driven and volatile. Rose would be good for him – he knew that categorically. They would spend the rest of their lives together. They would probably have children. And just as he had moved on from the emotional attachment that he had perhaps foolishly formed with Rose, she would grow to love the other 'him' and move forwards herself.

He hoped fervently that if they had a girl, they didn't call her 'Chardonnay'.

Then there had been the separation from Donna, something that the Doctor didn't think he would ever like to dwell on too much. He had not been proud of himself for what he had done to her, particularly in light of the fact that she had not wanted to be returned to her humdrum existence. But he could not have allowed the human-Time Lord meta-crisis to have destroyed her. She meant too much to him for that.

He flipped a switch on the TARDIS console moodily and stabbed a destination into the computer, absently bracing himself as the aged machine lurched violently in a different direction.

He could have let her continue as she was for a while. The idea of a matched mind, of a companion intellect had been sorely tempting – but the degradation had already become too far advanced. Had Donna been a dull-witted, empty-headed woman, the human portion of her brain would have fought for much longer against the encroaching accumulated knowledge of almost a millennia of space and time travel. But she was clever, Donna. Oh yes. Very clever and very, very human. No, he had done what he had done out of necessity and compassion. Nothing more, nothing less.

He nodded abruptly. Yes, that was right. Compassion. Despite the tears and the terror in her eyes when he had taken the memories from her. It had been an action of compassion.

"Donna...I'm just leaving."

"Yeah. See ya."

The Doctor closed his eyes. It had been hard to leave her like that. It was as though he had taken everything good from her and left her with nothing. At least she had the support of her family. Wilf would see her through and he suspected that even Donna's mother might now learn to see her daughter in a new light. But he also knew well enough that time would settle Donna back to normal, that she would ultimately reach her full human potential, whether that be as a temp in a library, or even as Prime Minister, should the dice of Fate be cast that way.

Prime Minister.

Harriet Jones.

Yes, he knew who she was.

The woman whose entire government he had deposed with six little words murmured into the ear of an aide. The woman whose reasoning that someday the Earth would be in trouble and the Doctor wouldn't be there to help had been flawless and the woman who he had all but scratched from his memory in bitter anger as a result of her hostile actions against the Sycorax. The woman who had never once given up hope – but who had given up her life just so that he might be found.

He felt more shame for his treatment of Harriet Jones than anything he could remember for a very long time. It had been so very indicative of the earlier behaviour of this incarnation and he realised, with some very small comfort, that he had undoubtedly changed exponentially since then.

Captain Jack and Martha – they were constants. They never seemed to change, not really. Only Martha was starting to become something that made the Doctor nervous deep down. She had gone from being a poised, competent, strong willed young woman to becoming UNIT's pawn – whether she realised it or not. He suspected that in time, he would run into Doctor Jones again. He hoped fervently that they were fighting on the same side.

Jack Harkness, he knew with great satisfaction, would never change. There were some things in life that could be relied upon. Death (although not in Jack's case, obviously), taxes, Slade at Christmas and Jack making an inappropriate sexual innuendo at the most inappropriate of times. He had grown quite fond of the time agent – not that he would ever admit it out loud.

And Sarah Jane Smith. The Doctor smiled as he remembered the joy and excitement on her face when she had left to return home to her son. There was a story there that the Doctor felt almost offended that he wasn't a part of – perhaps the details were something he could acquire and fill in at some other time.

Some other time it would have to be. Because right now, the Doctor wanted to be nowhere near the Earth. Martha and Jack, along with Mr Smith now had the means to communicate with him should things be desperate, but right now, the Earth was the very last place in the cosmos that he wanted to be anywhere near. He had an entirely different destination in mind. He didn't particularly want to go there, but it was a necessity.

"Just you and me again, old girl," he said to the TARDIS, a tone of forced cheerfulness in his voice. He rested a hand on the console and the TARDIS thrummed gently under his touch. A real sense of home and comfort filled him and he allowed the familiar sounds of his TARDIS to dissipate all the negativity of what had happened. His soul lightened. So what if he was the 'Destroyer of Worlds'? He rested a hand on the engaging lever and nodded once again.

"Sticks and stones," he said with a sudden grin, "may break my bones, but randomly assigned monikers doled out by a crazed madman working at the behest of an insane Dalek based on the actions of a cloned half-human-half-Time-Lord-half-a-pint-of-lager-and-a-packet-of-crisps-please who was acting out of a selfless need to defend the entire human race and beyond..." His lips moved as he tried to catch up with himself. "...may never hurt me."

Having so declaimed, he slammed up the lever and the TARDIS sped through space towards the Shadow Proclamation.

(Continues in Chapter Two)