The younger Doctor held up a slightly bent, lozenge-shaped metallic component between his hands and the others clustered round, the elder Doctor wobbling to his feet with the help of his stick and making his way over to join them.
"What is it?" asked Jeff, interested as always.
"It's the automatic guidance system from our tame Skypig. As you know the Doctor and I had planned to reprogram it to do our bidding, but as you can see..."
He held it up as if the difficulty would be obvious to anyone. Anna shook her head with an exasperated curl of her lip.
"What my youthful alter-ego is trying to say," the elder Doctor spoke up, "Is that the quadriphasic filternodes are clearly repilitated."
"That's still not really very helpful," Jasmine told him.
"To put it another way," the younger said, "It's broken."
There was a collective "Ah" from the assembled companions.
"Can't you fix it?" Anna asked.
"Given time, certainly. We could build a new one, in fact, much better than this. However..."
The others followed his gaze as he glanced up over the tops of the surrounding trees. A seething blade of light was clearly visible slicing up from the horizon into the clouds, splitting the sky into two halves.
"What's that?" Jasmine whispered.
"It's the beginning," said the elder Doctor, "Of the end of the world."
Everyone turned to look at him and he seemed a little embarrassed by this outrageous piece of melodrama.
"Well, I'm sorry, but it is."
"He's right," the younger confirmed. "Krongeist is beginning to break through. If we're going to make this work we need to move right now."
"But we can't, can we?" said Jeff. "You said we can't control the Skypig."
"I said the automatic guidance system was broken. But there is one other way we might control it."
Slowly, he drew something from his pocket. Jeff looked at it blankly.
"String." It was indeed a long, wiggly piece of string, frayed in places, that looked like it had been used for many different purposes already. "Sorry, Doctor, I'm not following."
"You surprise me. It's a piece of engineering very much on your level. We attach one end of this piece of string to each of the Skypig's manoeuvring thrusters, and we steer it that way."
"But to do that," said Jeff slowly, feeling his way along, "You'd have to be..."
"Sitting on the Skypig's back, yes."
"And when you flew into that rift thing, you'd be..."
"Killed instantly, yes."
With a sharp intake of breath Jasmine grasped what he was suggesting.
"Doctor, you can't!"
He was quite calm and serious when he looked down at her.
"Actually, Jasmine, I wasn't volunteering."
His gaze swept slowly across the group, to settle remorselessly on Jeff.
"Me?" The young man drew back, stuttering as he sought the words. "I... I... well..."
Anna's furious voice cut across him, her blue eyes like fire and ice.
"Who the hell do you think you are? It's your stupid plan, do it your own damn self! How dare you try and push Jeff into this? You..."
"He may be right."
The elder Doctor's quiet words silenced her instantly, and she turned to him, disbelieving.
"Doctor!"
"It's not as it seems," he told her gravely. "Jasmine and my future self arrived on Agrathus after the time distortion had come into effect. They're like outside observers to the whole phenomenon, which is why Jasmine could see things changing in the town which none of the local residents were aware of. The three of us, however, have been here from the start. We are part of this unstable timeline, which means that if we die it really doesn't signify that much, because if this plan succeeds and the timeline is deleted, then our deaths will be eradicated along with everything else."
"You're saying..." Jeff frowned, "That if I do this, and get killed, I'll just come back to life again?"
"More or less. All will be as it would have been if the Skypigs had never been sent back in time. We'll have no memory of any of these events because, from our perspective, they will never have occurred. Jasmine and the other Doctor, on the other hand will remember everything, because, as I said, they are observers to the distortion and not participants." His aged face crumpled in a sympathetic way, and he tapped a wrinkled finger against his forehead. "It's all very complicated and the human mind isn't really built for these concepts. As you yourself have often said, sometimes it's best just to assume the Doctor knows what he's talking about and get on with it."
Jeff smiled reluctantly.
"I didn't know you were listening when I said that." He took a deep breath and ruffled a hand through his soft brown hair. "Oh well. I suppose I'd better do it, then."
"I'll come with you," said Anna.
He looked at her, genuinely surprised.
"Really?"
She shrugged.
"Someone has to make sure you don't fall off."
"It's a good idea," the younger Doctor said. His voice was low, like at a funeral. He glanced over at where the balloon, propped over the burner on the Skypig's back, was steadily gaining buoyancy from the accumulated hot air, and twisted the string between his fingers. "Well. Let's get knotting."