The wizards left the building and made their way to the nearest open space, a market square that was currently empty except for a handful of pedestrians who stared at them curiously as they strolled past. They unpacked their flying carpets for the short flight to the horseshoe dike, but they were still unrolling them flat on the ground when a worried looking official arrived, accompanied by a troop of soldiers.

     "Are you leaving us so soon?" he asked, making no attempt to disguise his relief. "I trust your visit to our city was pleasant and productive."

     "Eminently so," agreed Saturn, deciding not to disillusion him. "Please convey my apologies to the Archchancellor and tell him I won't be able to join him for dinner after all."

     "He'll be most disappointed," said the official. "He was looking forward to your company, to finding out something of what's going on in Amafryka these days."

     "You can tell him that nothing of any consequence is going on in Amafryka," replied the wizard, taking his place on the carpet while the other four wizards sat crowded together on the other. He saw Galia emerging from the museum and hurrying across to the town hall where she would, no doubt, report their interest in the horseshoe dike. Would the city officials guess that their visitors would be heading there to examine the place for themselves? They would have to hurry if they weren't to be accompanied all the way by city troops. As it was, soldiers would no doubt be arriving within a few hours, to 'protect their honoured guests from the perils of the open countryside'.

     "Thank you for the assistance you've given us and your warm hospitality," said Saturn, therefore, and he gave the command for the carpet to rise.

     As they moved off towards the north, Thomas looked back and saw a functionary running from the town hall towards the official they'd just been speaking to, and then both men and the soldiers hurried to the stables.

    He saw Saturn scowling in annoyance and mutter something to himself. Thomas translated it by reading his lips. "We're leaving their city," the elderly wizard was saying. "What did they care what we do in an ancient archaeological site?"

     Thomas nodded with agreement. Perhaps they thought they'd come to steal away some long hidden treasure that the Archchancellor thought belonged to the city. He chuckled as he thought of the shards of pottery and lumps of rusty metal which was all they were likely to find. Would the Archchancellor demand they be carried away for safe keeping in the city's vaults? On the other carpet, Saturn urged the carpet to its maximum speed and Thomas did the same. With luck, they'd have finished what they came for and be gone by the time the soldiers arrived.

     The horseshoe dike wasn't hard to find. The low, broad dike ran in a long, gentle curve across the pastureland on which a small group of cattle grazed contentedly, looking up disinterestedly at the carpets as they passed overhead. The ground was wide and flat, except to the south there it fell away in a gentle slope to another plain twenty yards below. The ancient shoreline, thought Thomas. Once, water had lapped against that slope, which had no doubt been a sandy beach with clumps of seaweed stranded on the tideline. There were gulls circling overhead, signifying that, even today, the sea wasn't too far away, and looking to the south he thought he could just barely make out a thin strip of silver between the flat horizon and the light blue sky. Sixteen thousand years! he thought in wonder. He found it hard to even imagine such an immense stretch of time.

     Saturn flew his carpet back and forth across the site a couple of times before landing, looking for changes in grass height and colouration that would testify to changes in the underlying soil. Thomas, on the other carpet, saw rectangular patches of greener, taller grass in the centre of the circular area contained by the dike, but Thomas thought they were most likely to be the remains of previous digs. They also saw the remains of fairly recent buildings. Lines of stones. The remains of walls and enclosures, but they could be, at most, only a couple of hundred years old and all five wizards dismissed them without a thought.

     As they were flying out to the north of the dike, though, circling around for another pass, Thomas was suddenly struck by the overwhelming sense that he'd seen this landscape before. It was something to do with the line of low hills crossing the horizon ahead of them, and the ice capped mountains rising behind them. There was something about that view. Something deeply familiar...

     Suddenly it came to him. The images displayed by Gannlow's artifact. The magical diary or whatever it had been. This was where those pictures had been taken, without a shadow of a doubt. Here, but sixteen thousand years before.

     He tried to remember the details of those images. Huge fields of grain and other crops so great that their fenced boundaries could barely be seen in the distance, tended by gigantic creatures of metal and glass that rolled slowly along on wheels taller than the tallest man. Beyond the fields were endless acres of scorched wasteland where fire had been used to clear the wild growth, and beyond that had been the wilderness. A forest that he'd been astonished to see was composed entirely of purple plants. It had been as if the purple plants had enjoyed undisputed mastery of the world and had had to be cleared to make way for the familiar green vegetation he was used to.

     An idea he'd had before came back to him. Most sages and wizards believed that man had originated independently on every world. Created by Gods that lacked an imagination, perhaps, and who simply stuck to a tried and tested formula. While exploring the planet Veglia, though, he had wondered whether man had originated only once, on one world, and spread to all the others, either by walking the planes of existence or by means of ships of space, or both.

     If that were so, then sixteen thousand years ago would have been the time his ancestors had first arrived on Tharia. They'd found a world covered by animals and plants deadly poisonous to human life and had struggled hard to establish friendly green plants in the hostile, alien soil. Maybe Agromay had been their first city, their bridgehead, or maybe they'd established several settlements across the world of which Agromay was the only one of which any trace remained. Then, maybe caused in some way by the opening of the space portal, their civilisation, and that of the Ringbuilders and the Citybuilders, had been destroyed. They'd been thrown back to a simpler existence, having to live as part of the natural world instead of being the masters of it, and as thousands of years had passed they'd gradually split and divided into the dozens of humanoid races inhabiting the world today.

     He smiled to himself. It was an interesting theory, but he didn't think Saturn would think much of it. He would demand to know how the Worlds of the Sheaf could have been colonized before the portal existed. He frowned unhappily. Maybe they'd find some clue to the mystery in the horseshoe dike, or maybe he'd think of something that would make the thing clear.

     The two carpets banked around to return to the dike and prepared for a landing. As they approached the long, curving dike Thomas saw it again as Tak had seen it. Not a dike but a wall. Impossibly tall and powerful and spaced with towers bristling with weapons of fire and lightning that they used to defend themselves against the fearsome creatures that had roamed the planet in those days. Creatures that now existed only as fossils.

     He remembered that battle that had been recorded in Gannlow’s artifact, the creatures so huge that even dragons would have been afraid of them. The battle that had taken his breath away as the ground shook and the air thundered. What must it have been like to have lived in that city, hearing the battle taking place? Desperately praying that the creatures didn’t break through the defences, to the ruin of everything? What had possessed them to colonise such a dangerous planet? Were they brave and bold, confident in their ability to overcome any opposition? Or were they desperate?

     Saturn landed his carpet just inside the dike and Thomas landed the other just beside it. The elder wizard was already striding up and down, studying the grass under his feet as if he could see through it to whatever traces of the city might still be down there.

     "The centre of the enclosed area has already been examined," he said, more to himself than the other wizards. "They assumed the settlement was arranged along the lines of a conventional city and dug where they thought the public buildings would have been."

     "A logical assumption," said Braddle. "Do you suspect this was not a conventional city, then?"

     "I think it was a colony. A bridgehead in hostile territory. Whoever these people were, they may have come from one of the worlds lacking magic. Imagine their shock and horror at coming face to face with dragons, hydrae, basilisks etcetera if they'd never encountered such creatures before. Something that can turn a man to stone with a single gaze. Can you imagine the terror? The stark disbelief if they'd had no idea such a thing was possible? I suspect that was the reason for the dike, or the wall as it probably was back then. They thought they'd be able to protect themselves behind steel and concrete."

     Thomas nodded. It made sense, and it might even explain what had happened to them. Only magic could provide an adequate defence against some of the creatures living on and in Tharia, but if that was what had happened, how had any of those first humans survived at all? He trembled with excitement. Could they have invented wizardry in the time they'd had between the building of the settlement and its destruction? Could the very first wizards have lived within the curve of this dike?

     He gave voice to this thought, only for Saturn to give a noncommittal grunt and stride away, muttering under his breath. Braddle looked interested, though. "The very cradle of wizardry!" he said, gazing around as if he could actually see those first pioneers at work in their laboratories. "Maybe here we'll find the answer to that ancient riddle. If wizards can only learn their art by being taught by an older wizard, then how did the first wizards get started? The only theory I've ever thought even halfway acceptable is that they were taught by an older, prehuman race, but even that has problems. Who were these prehumans? And why do we find no trace of them today?

     "Maybe we'll find something here," suggested Lirenna, and the others nodded hopefully.

     Saturn returned a few moments later. "I can find nothing to suggest a likely spot," he said dejectedly. "Others have been here before us and found nothing but the few artifacts we found in the museum. I think it's clear that only a complete excavation of the entire area stands a hope of finding anything new." He looked at Braddle. "Unless, that is, our diviner is able to offer any insights."

     The nome shook his head, though. "The paramorphic traces decayed long, long ago," he said. "The only way to find anything now would be to physically dig down and look, but this is an area of at least a dozen square miles. Finding a needle in a haystack would be childsplay in comparison."

     Saturn nodded. "Maybe something will occur to us later. Now that we've been here, we'll be able to teleport back any time we want, once the last trace of the interference has vanished. Until then, I think it best to leave this site pristine, to preserve whatever evidence might be down there." He walked slowly back towards his carpet, his head lowered and his hands clasped behind his back, deep in thought.

     "We'd better be going as well," said Lirenna. "I can hear hoofbeats. I think the men from the city are nearly here."

     Thomas nodded and took his place on the carpet as the others crowded on beside him. The Grommans would want to know what they were doing here, and although the wizards had nothing to hide they didn't fancy wasting a lot of time with lengthy explanations. It would be a lot simpler if they were gone before the soldiers arrived. If they came back, a few weeks or months from now, they wouldn't bother with the city but would come straight to the horseshoe dike without alerting anyone to their presence. They'd be able to work in peace, at their leisure.

     Would they be coming back? wondered Thomas, feeling Lirenna steadying herself against him as the carpet lifted. Yes, of course they would. Even Saturn was now convinced that a primordial civilisation had existed on Tharia sixteen thousand years ago. A civilisation from which every civilisation now existing on their world was descended, and it was now almost certain that it had been destroyed, along with at least two others and maybe many more on other worlds, by a disaster of truly cosmic proportions. They had to know what had happened, because if it had happened once, it might happen again at any time. Maybe tomorrow.

     He found himself looking up at Derro, the red sun glowering down at him with an almost palpable sense of malice. He wished he could rid himself of the feeling that Derro was somehow responsible, because the red sun was so colossal, so powerful, that surely no force in the universe could protect them if it decided to lash out at them...

     He put the thought out of his head and concentrated on the journey back to the Fellowship's teleportation cubicle, but there was still a frown of worry on his face as the carpet gained height and sped across the verdant Garonian countryside.

☆☆☆

     Two weeks later, the Jules Verne passed through the portal again, on its way to visit the planet of the Shipbuilders. Thomas was aboard, for what he expected to be his last mission aboard the Ship of Space, and Lirenna was with him, as was Tassley, Saturn, Braddle Bandock, Timothy Birch and Drenn Pietar. Matthew, however, wasn't aboard. Another cavalry Flight Leader, Titus Drusero, had been brought in to replace him, and Thomas was missing his friend even before the portal had shrunk to a dot behind them. He missed the talks they'd had. The easy, comfortable way he'd been able to open his soul to him and say things he couldn't have told anyone else.

     He had no right to hoard the man, though. His wife, Heather, and his children had a much greater claim on him and Thomas smiled fondly as he imagined the newly reunited family. The four of them talking and playing together. Enjoying meals together. Generally making up for lost time. That'll be us soon, he thought longingly as he and Lirenna sat in his cabin, their arms around each other. As soon as this mission's over we'll say goodbye to Lexandria and go back to Haven. Home.

     He smiled at the thought, and mentally willed the ship to greater speed. The sooner we get there, he thought, the sooner we get back. It might be as little as a couple of weeks.

     Lirenna looked at him, and Thomas saw the very same thoughts passing through her head. They smiled at each other, simply enjoying each other's company as the Jules Verne sped through space at ever greater speed. Racing towards the source of the mystery that had so alarmed the University ever since the Rossem meteorite had first been discovered, all those years before.