KNOW THINE ENEMY

The city was whole. In the town square many buildings stretched up toward the clouds, and beyond. It was a clear bright day. Everything was peaceful, and for a telepathic species, quiet. From simple nods of their heads, the people of Vestigualamavundar could hold complete conversations in seconds. Sarah could hear the language in her own mind; not dissimilar to that of Earth, though some words were unintelligible.

Then an alien sound began to permeate the stillness of the day, and with that sound came a tension so tangible that Sarah could feel it touch her. She recognised the time vessel as a TARDIS, appearing to her in her mind's eye as an ionic column. The stranger who stepped from it was dressed simply in tunic and breeches, his hair short and dark, the eyes keen and intelligent.

A crowd began to gather around this new arrival. The Doctor, for Sarah knew it was he, smiled at the mass of people. He made as if to speak, then paused, remembering the etiquette on such occasions.

"GREETINGS. I COME AS A FRIEND."

The mental energy from those initial words was deafening, even to Sarah. Those nearest to the Time Lord fell to the ground, their mental defences crushed. Within seconds their bodies were lifeless.

The Doctor was shocked. "WHAT'S HAPPENING?" His telepathic power cut through like a knife, killing everything in its path. Too late, the Doctor realised his mistake. But even his random thoughts, concern for those fallen, followed on like a virulent plague, destroying all who came into contact. "No, please! I didn't know!" All around him, the story was the same. And there was no respite, no save haven. A once proud civilisation was decimated in less than a minute. Only the Doctor was left, sitting dejectedly on the stone steps, head in his hands, crying for the dead.

"Sarah! Sarah, come back!" With an effort, Sarah pulled her hand away from the book. The dizziness was stronger this time, and it took a few moments for her to recover. It was all she could do to keep the tremor from her voice as she spoke. "All those people . . ."

"I know, Sarah. I know." The Doctor's voice was heavy with emotion. "You know now why the Master wiped all records of this place, and why I couldn't tell you the truth once I remembered.

"I thought I knew it all - doesn't every child think they know all the answers at some stage in their life? And that's what I was, Sarah. A foolish, unthinking child. I was grateful for the Master's friendship then. He saved me from myself."

"And how do you feel now?"

"Now?" He thought long and hard. "Purged, I suppose. Like a huge weight has been lifted from me. It's like you said, Sarah - we all have to face our demons. We just don't like to admit our mistakes."

"Just so long as we can learn from them, Doctor," Sarah observed.

"Yes." The Doctor looked up at the roof of the Tower. "You know, it's amazing how this has stood intact all this time."

"Like a monument," Sarah agreed.

"Hmm. Or . . ." He paused, deep in thought. "A monument, or a beacon? I wonder . . ." He began to pace backwards and forwards up and down the aisle, until he stopped, a look of incredulity on his face. "Sarah, you are amazing!"

"I am?"

He nodded. "With a whole planet to search, you brought us to the only spot where the next missing component could possibly be!"

The Doctor looked around himself waiting for inspiration to direct him. Sitting on a table amongst the shelves was a book. This was a normal paper and pages book and not of the local energy variety. Sarah looked where the Doctor's gaze had fallen and realised what he was thinking. What could be more natural than a book on a library. As they moved closer to the book they noticed it was a copy of Alice in Wonderland.

"How like the old girl," the Doctor approved.

They smiled at each other as the Doctor stretched out his hand and touched the book. Then, just like the cyber head on Telos, the book transformed itself into a complex looking component, which the Doctor recognised as the time vector generator. A moment later the familiar sound of the Master materialising could be heard.

"Sarah, I think I know who is behind all this," said the Doctor. "The body swap, being pulled into the vortex and the Master being sent to help us."

There wasn't much time. "Quick, tell me before the Master fully materialises," said Sarah.

The Doctor opened his mouth to speak but was suddenly frozen before he could get out the words. Sarah looked to the Master but he too was frozen, half in this world and half in the vortex. It was as though everything around her was paused like an image on a video.

"Well, my dear Sarah Jane. Looks like the old fella has finally twigged," said a familiar voice.

She spun round to see where the voice had come from. She recognised the voice instantly, but she was unprepared for the sight behind her. There he was, totally recognisable but different. The same face, but scared and older. The same voice, but huskier. Similar clothing, but all in black. He grinned back at her, enjoying her discomfort. Those same big white teeth in the same smile, but the expression was much more malignant.

"Let me introduce myself, Sarah, I am the Doctor - the real Doctor. The version of myself that would have existed had the Master not wiped my memory of the events on this planet.

"While this feeble fool learned to love peace and knowledge free from the guilt of his actions here, I went on to learn to love the chaos and pain of the genocide I committed here. Finally, I am reclaiming my existence."

Sarah shook her head defiantly. "No, you can't be the Doctor. I know him." She indicated his frozen form. "He's a good man."

The Dark Doctor approached her, but she kept a safe distance. "My dear Sarah, that do-gooder is nothing but a pale imitation of me. You must believe me."

Sarah's mind was turning cartwheels. Either this version of the Doctor was telling the truth, or he was just spinning a lie. Whatever the case, she needed answers. "Alright. How did you find us?"

"Oh, the obligatory questions," he laughed. "Very well." He sat down upon the stone steps. "When I returned to Gallifrey, it was with the intent of learning all I could about our depraved culture. I discovered so much, particularly about their macabre forms of entertainment. Did you know that there was a place called the Death Zone? They used it as a kind of testing ground for other life forms, delivering them to the Zone by use of a Time Scoop. Later, they forbade use of it and turned their attention to other worlds, becoming the timid observers of today.

"But they never thought to do away with the machinery itself. So I bided my time, and waited." He indicated the frozen Doctor. "It was childsplay for me to track you and he through the vortex. Then once I had access to the Time Scoop, it was just a matter of plucking you out of time and depositing you on Atora. Simple, really."

Sarah took all this in. "So you were responsible for that body swap we went through?"

"Ah, yes. That was an unfortunate mistake on my part. It's like anything you try - you don't always get it right first time."

"Well, thanks very much. You make it sound like a laboratory experiment." Sarah was angry now.

He smiled. "I suppose it was, in a way. But the end result was going to be the same. Once the Master had set the Doctor on his search for those TARDIS components, it was only a matter of time before you turned up here."

"And I suppose the Master knew all about this?"

"Oh, no," he replied. "That was the irony of it. He truly believed he was helping the Doctor, and was working as an agent for the High Council of the Time Lords. Such a simple deception. Now, enough questions."

He rose from his sitting position, rising to his full height. "It's time for me to pick up where the good Doctor left off - with you at my side, Sarah."

"What do you mean?" she asked.

"This is an ideal time for me to step into this universe and take over from this fop," he replied. "His goody two shoes reputation will allow me access to the most sacred halls and private quarters of the most important people in all space and time. I will play with them, send their cultures in different directions, pollute their ideals with foreign ideas until I remake the universe in a form that amuses me."

"While the universe continues to think you are trying to save everyone?"

"Exactly, Sarah. At the moment my existence is fragile, but the more I shape the universe into one that suits my own time line then I become more real, and your Doctor will cease to have ever existed."

"And then what?" asked Sarah. "When you are real and the universe is remade, what will you do then?"

"Why, start to tear it apart of course," as if the answer was obvious.

"Why?"

"For the sheer unbridled fun of it. I got a taste for destruction on this very planet."

There was a sudden gurgling noise behind Sarah and she turned towards it to see what it was. Horrified, she watched as the Doctor - her Doctor - began to strain against the time field holding him. The movement were slight, imperceptible at first. But as they gradually became more pronounced, the Doctor's dark persona stepped forward, a look of shock on his face. "No, it's impossible. This is against all known phenomena."

The Doctor forced a smile. When he spoke the words came out through a wall of static. They were blurred, but recognisable. "Unknown phenomena has always been a speciality of mine." He called out. "Sarah!"

She needed no second bidding and ran across to him. "I'm here, Doctor. What do I do?"

"Take my hand."

"No!" Sarah hesitated at the Dark Doctor's voice. "He is weak. Touch him and he dies."

She glared at him defiantly. "No, he is strong, and a better man than you."

"You'll die too," he insisted.

"Then I'll take that chance. Because if I don't, how many more deaths will there be?" Resolute, she took the Doctor's hand in hers. As their hands touched, a swell of Artron energy coursed through both their bodies. Sarah held on tightly as the energy build up grew and forced its way outward, spiralling around them.

"Hold on, Sarah. It's nearly over." The Doctor's voice was clearer this time, as the energy began to lose its strength. Gradually the spiral effect reduced in power, and the molecules surrounding them dissipated and faded away to nothing.

All was still. The Doctor let out a breath. "Phew! That was a near thing." He smiled down at his companion. "Thank you, Sarah."

She returned the smile. "Anytime, Doctor."

"Nooo!!" The two friends were thrown to the floor as the Dark Doctor pushed past them, running down the aisle they had entered.

"He'll be running for his TARDIS," the Doctor realised. "Sarah, get the time vector generator and attend to the Master."

"Right." She paused. "Hang on, what about you?"

"I'll be back, don't worry." He set off after his dark persona.

Sarah quickly grabbed the component as, with the Dark Doctor's control now broken, the Master finally completed his materialisation. He staggered for a moment, and Sarah took his arm to steady him.

For once he was grateful for someone's help, though he was glad that the Doctor wasn't around to notice. "Thank you, Miss Smith. What happened?"

"I'll explain later," she promised. "Right now, the Doctor's in trouble. This way." She led him down the long corridor, up the spiral staircase, all the while following the Doctor toward the Tower's main doors. By the time they had caught him up, the Doctor was alone in the main courtyard, kicking his heels and fuming. Sarah knew she didn't have to ask.

"He's gone, Sarah. I missed him by a nanosecond."

"Oh, Doctor."

"If it's not too much trouble," inquired the Master, "will someone please tell me exactly what is going on?"

The Doctor sighed. "You could say our problems have just become a whole lot worse."