"An alternate timeline?" asked Alison.
"No, no, no! The Doctor nearly shouted with glee. "A redundant time line, a sort of temporal eddy, or bubble of unreality if you will."
"And we're in it?"
"We are it!" He grinned broadly and stretched his arms out indicating the entire console room and it's three occupants.
The Doctor's unusual exuberance made Alison nervous. "How can you be certain?" She gazed at the boiling red depression that hung placidly in the center of the Tardis view screen.
"My dear girl," the Master interrupted "he can be certain because he has eyes."
"Oh well that explains everything" Alison said blandly.
The Doctor smiled and indicated the scarlet monstrosity shifting silently in it's background of twinkling stars. "It's a time well," he explained "and it exists in an actual physical location, just as you see it now..."
"Yes..." Alison eyed the screen suspiciously.
"but it's also a temporal construct, a theoretical..."
"This really isn't helping" said Alison.
The Doctor leapt toward the console. He pressed a button and the view screen was filled with the red glow. "In normal space-time the effect wouldn't be visible. It could only be located mathematically, and only then by an extremely advanced computer or by a being with exceptional intelligence."
"Which is why he believed only he could locate it" said the Master.
"Well I have haven't I?"
"Only by shear accident."
"Wait... wait..." Alison sighed "before you two start arguing again, let me get this strait. In normal reality I wouldn't be able to see it?"
"Exactly" The Doctor and Master answered in unison.
"Because it doesn't exist."
"Correct."
"And yet it does."
"To some extent yes." The Doctor answered "Think of it as the hub of a wheel, a universal focal point that extents into every conceivable reality. Parts of it do exist in your dimension but it's beyond your ability to sense it.
"And its shrinking" said Alison as she pointed to the view screen. The outer edge of the thing was slowly fading to black, the redness slowly pouring in on itself like shifting sand.
"Of course" the Doctor whispered.
Alison squinted at the screen "What does it mean?"
The Master stepped forward. "It means, that unless we do something the well will close, and this temporal anomaly that we happen to be so intricate a part of will cease to exist."
Alison looked to the Doctor "What can we do about it?"
"Do? We're not going to do anything." Her eyes widened, and he smiled in response. "Alison you don't seem to understand, there is no real risk. We'll all still continue to exist, you back on earth and myself, well... I'll still be around, just not as the man I am now."
"Simple as that?" her brows raised.
"These things occur naturally..." he explained patiently "picture a stone being dropped in a pond. Ripples move outward from the point of impact and then return to the source." He turned to look at the screen once more and rubbed his chin thoughtfully. "Hmmmm... perhaps it is no mistake that we located it."
"And these "ripples" move both into the past and the future?" she asked.
"Indeed" the Master replied "causing relatively mild time discrepancies that eventually merge with the normal time line."
"I see" she said softly.
"So now, we sit back and watch" the Doctor said. "Just think Alison, you'll be the only human in existence to have witnessed a spectacle like this."
"Though you'll have no memory of it of course" the Master added helpfully.
"So we just watch it close."
The Doctor nodded "There's nothing we could do to stop it anyway."
"That is not entirely correct" said the Master. The Doctor turned to face him. "I have my own theory on the matter."
"Which is?" the Doctor asked with interest.
"That if one could survive in the center of the well, one could conceivably exert some mental control over its activity, and as it is linked to all reality... all time..."
"One could rationalize the anomaly, create a new, stable timeline." The Doctor considered it for a moment and shook his head "No living body could survive..." he stopped and stared at the Master who's face was locked in a tight smile.
"Well..." he said slowly "well... you have a point, but I could never allow you to do that."
"Why not" asked Alison.
"Because in this particular instance he wouldn't be creating an alternate thread, he'd be obliterating the original."
"... to no great loss." the Master added.
The Doctor glanced from the Master to Alison in turns. Finally his eyes rested on the Master. "It's not going to happen."
The Master's eyes moved downward though the smile never left his face. "I thought not."
A silence fell over the console room.
"Well, now that that's settled" said the Doctor quietly "I think I'll bring up some extra chairs, the view should be spectacular." He took one last look at the both of them and then turned and left the room.