Thinking about that made Polly’s head ache. She turned onto the track and headed towards the human sounds. Shortly a covered wagon rounded a corner, pulled into view by a big white shire horse. The vehicle was hung with the bells she had heard, and painted with the words ‘The Amazing Berthold’ and its woodwork was intricately carved. Polly paused in its path as it approached, the driver and his elderly companion peering at her suspiciously, then she moved to one side of the track. As the wagon drew alongside her, she observed a young dark-haired man holding the reins, his clothes straight out of some historical interactive, and his broad flat hat sporting a couple of pheasant feathers. He pulled on the reins to halt the horse, then reached down to haul up the wooden brake.
At last it was ending, and the world was returning in coloured flashes like a strange species of lightning. Gradually revealed through the mantisal’s glassy spars was a landscape seemingly little different from the one they had recently departed. They rematerialized above grassland a few hundred metres away from the edge of dense forest. Then Tack began to note the subtle but disturbing differences. Here the cloud-dotted sky was a deeper blue, the green of sprouting grass was hazing up through the trampled sea of older stalks, and everywhere were scattered yellow, red and lavender flowers. The distant trees were also tinged with the green and yellow of new growth, and there were birds racketing up into the air. A balmy breeze, carrying with it the smells of hot spring, dispersed the cold from the skeletal cage of the mantisal.
‘Best get to the trees as quickly as we can,’ said Traveller. ‘Out here we’re likely to get stomped.’
Tack saw that the man was tired again and his eyes lifeless. Traveller gestured to a distant elephantine shape coming towards them.
‘Mammoth,’ Tack said.
Traveller snorted. ‘Wrong. They’re ten million years in the future. That thing over there is a deinotherium—a rather larger and more bad-tempered ancestor of the elephant. So let’s move.’
They dropped out of the mantisal and walked away from it. Glancing back, Tack saw the strange thing fold out of existence, leaving a cold mist that swiftly dissipated. Nearby he saw huge skins of excrement covering the ground, some old enough for plants to be pushing up through them, and some new enough to be covered by legions of flies contesting ownership with dung beetles the size of golf balls. Avoiding these, they tramped on towards the trees, keeping a wary eye on the approaching beast.
‘How big is it? I can’t really tell,’ Tack asked.
‘About four metres high at the shoulder. We could bring it down with our weapons, but even this far back in time every drastic action we take creates difficulties for the mantisal.’ Seeing Tack’s puzzled expression Traveller went on, ‘We come from the potential future, and no matter how careful we may be our actions here affect that future.’ He gestured all about them. ‘Our presence here is even now moving this time-line down the probability slope, leaving as the main line all this without our presence. Therefore, in each jump through time we make, the mantisal takes us not only back in time but back up the slope to mainline time. And the more we influence each time we are in, thus affecting our probable future, the more slope it has to carry us back up on the next jump. Luckily, the further back we go, the less we affect our probable future.’
Reflecting on their previous conversations, Tack said, ‘I’d have thought the danger would increase the further back we went.’
His expression showing his customary irritation, Traveller glanced across at him. ‘Which shows just how little you understand. As I said before: kill your father before your conception and you’ll end up right down the slope, where it would take the full energy output of the sun tap for a whole day to propel you back onto the main line. But to achieve the same screw-up here, you’d need heavy weapons—and as far back as, say, the Jurassic, nothing less than a tactical nuke.’
‘I don’t understand.’
‘No, of course not.’ Traveller said nothing more for a while then, relenting, added, ‘Errors like that do not accumulate through time. There’s an effect called temporal inertia. By travelling back in time and killing your father, you push yourself down the slope because of the paradox you’ve created. Kill your direct ancestor a hundred million years in the past, and you’ll still be born.’
‘But doesn’t that mean… predestination… some controlling intelligence?’
‘Only in the way that a tree is predestined to grow towards the sun, and only in the way that some god might have made that tree. Evolutionary forces are macroscale as well as microscale.’
‘But—’
‘Enough. Just think about what I’ve already told you. It is doubtful you’ll be able to understand it all anyway. You still think linear.’ Just then the deinotherium let out a roar and was suddenly charging towards them, kicking up a cloud of dust.
‘It is probably in must,’ said Traveller. ‘Pick up your pace.’
Tack did so readily, glancing back the way they had come as he broke into a trot. ‘Perhaps that’s pissed it off,’ he commented.
Traveller looked back, too, and his expression changed. The mantisal had returned, hovering just where they had previously abandoned it. Tack now did a double-take—it clearly wasn’t their mantisal, since it contained four individuals who were even now scrambling out of it.
‘Umbrathane,’ Traveller hissed. ‘Run!’
The order was reinforced through Tack’s programming, so without conscious volition he found himself obeying. As he ran he drew his seeker gun, and he wondered if he had received some subliminal instruction to do that as well. A triple flash to his side: Traveller was firing with that weapon of his, then sprinting past Tack to turn and fire again. Suddenly the grass to their right was burning and the air full of smoke. Again the deinotherium roared, and now they could feel the thunder of its progress.
‘Shed the pack!’
Still running, Tack obeyed, regretting the loss of the equipment it contained. But regret was dispelled when Traveller came sprinting past him with the same pack slung from one shoulder, as if its weight was of no consequence. Tack glanced back and saw the four newcomers heading directly towards them. Then the elephantine mass of the enraged animal thundered in between, drawing a veil of dust between them and their pursuers.
‘Move faster!’
From somewhere inside himself, Tack found his last few ergs of energy and accelerated. But no matter how fast he ran, or dodged from side to side, Traveller was in front of him, behind him, to the side, crouching and firing, then up again and sprinting away. Traveller was fast, more so than any human Tack knew of, and the man made Tack feel slow and clumsy, which he had never felt before.
Behind them, the deinotherium’s aggressive roaring changed to a panicked trumpeting, and Tack glimpsed back to see it turning aside, smoke boiling off its hindquarters, as black-clad figures moved quickly past it. Suddenly a tree exploded to Tack’s left, and it was only then that he realized they had finally reached the forest. Loud detonations and flashes continued to move off to his left—the direction Traveller had veered in as they entered the trees. Tack just kept running as hard as he could. In fact he could not stop, and knew that if Traveller did not cancel his last instruction soon, he, Tack, would die of a ruptured heart.
Stop.
The order at last came through Tack’s comlink as he was running, in the agony of lactic overload, down a black tunnel of trees. He immediately sprawled forwards on the ground, his muscles locking with cramps and his lungs feeling torn as he gasped for breath. Distantly he could still hear the trumpeting animal.