He was about to step through when he noticed that the red flag in the window had vanished and, looking back, he saw that the other door, the door he'd come in by, now had a red flag in its window. Going back to it, he found that it was now locked solidly shut, the wheel refusing to budge by as much as a single inch. “Yes, I know,” he muttered to himself. “When the red flag’s up, the door will only open when the other door’s shut. I just wish I knew why, that’s all.”

     As he heard his own voice in his ears, though, he froze as a new puzzle struck him. His voice was all wrong, unclear and distorted. Not sounding at all the way it should. And instead of the sound coming to his ears from outside, through the air, it seemed to be coming from inside his own head, as if it were travelling from his vocal chords to his eardrums directly via the bones of his skull instead of the more normal route. He puzzled over this for a few moments, talking and listening to the way it sounded, before shaking his head in perplexity and dismissing the problem as irrelevant.

     He stepped through the door and found himself in the huge cavern which, he now saw, was at least two hundred yards from the wall on his left to the one on his right, with rounded corners. The ceiling was twenty yards above his head, arched and buttressed to spread the weight of the rock above onto the walls and brilliantly lit with globes of glowing marble. Off to his right, though, he could see a huge crack in the ceiling. It was several yards wide at its widest point, rising up through hundreds of feet of solid moonrock until, way up at the top, he could see the faint light of stars shining down through it. At least he assumed they were stars, since they weren’t twinkling. Great piles of rubble lay beneath the crack, which extended all the way to the wall on his right, down the wall to the floor and, he was willing to bet, back along the floor towards him. Wow, thought the young soldier in amazement. There must have been an earthquake or something. I wonder if that’s why this place was abandoned?

     The cavern was filled with grass, shrubs and trees. It must have once been a park or something, but as he wandered around curiously he saw that everything was completely dead, the grass crunching under his feet like newly fallen snow. He touched the low hanging branch of a tree and it broke off in his hand, and when he squeezed it it crumbled to powder. “Weird,” he muttered to himself, and the sound of his voice in his head made him suddenly realise something even weirder. There was no sound in the cavern. It was totally silent. The grass crunching under his feet did so without making any sound, and the brittle twigs and branches he broke in his hand did so silently. What was more, when he kicked a pile of fallen leaves, they didn’t flutter back to the ground as leaves normally do but flew through the air and fell as though they were made of lead. “Weird,” he said again. “Tom’s going to love this place!”

     He continued walking, looking back every so often to make sure he didn’t lose sight of the door he’d come in through. Once, while he was looking back, he tripped over something, and when he looked down he gasped in horror to see that it was a human body. Badly mummified, its mouth open in a silent scream and its hands, held near its face, twisted into hooklike claws. It was clear to the astonished soldier that this man, whoever it had been, had died in agony.

     It was a gruesome sight but Matthew had seen worse and so he only stared curiously, wondering what had happened to him and whether it was anything he needed to worry about. Shortly after he came across another, an old man, and nearby was an empty pram, tipped over on its side but still containing a faded pink blanket as if the baby had been hurriedly snatched out by a frantic mother. Trapped under a tree that seemed to have been blown over in a storm (a storm in an underground cave? thought Matthew in bewilderment) was a small corpse dressed in the clothes of a young girl, held in the arms of an older male corpse, probably the father, as if offering comfort in the last moments of their lives.

     On the other side of a dry pond bed, a small group of older people, some in wheelchairs, lay slumped around a circular bandstand in which musical instruments had been abandoned, as if the calamity had struck while they’d been in the middle of a performance. The musicians had fled, along with most of the park’s other occupants, but the old folk and a few other unlucky individuals had been abandoned to their fates. Whatever had happened here had happened fast, then. There had been no time for rescuers to come to help those unable to help themselves.

     Elsewhere he saw more bodies, all in the same tortured, shrunken condition, and among them the evidence of a strong howling wind that had swept around them as they died. The young soldier remembered what the trogs had said about the air here being ‘dead’, their warnings that there was something terribly wrong with this place, and he broke out into a cold sweat, suddenly afraid that whatever death had struck here could do so again. The trogs were right, he thought as he looked around at the terrible scene. This is a bad place and we shouldn’t be here. I ought to go back to the others, warn them.

     He started to retrace his steps, but then noticed a row of five more closely spaced steel doors in the opposite wall of the cavern, hidden from his sight until then by a small grove of leafless, broken trees. This place must be bigger than he’d thought, he realised, and he decided to have a quick look to see what lay on their other side before he went back.

     It took just a couple of minutes to cross the rest of the park, during which he kept his eyes carefully fixed on the doors to avoid looking at the bodies all around him. When he reached the doors, though, he was shocked to see a small group of corpses gathered around them, frozen in the act of clawing at the wheels as if desperate to open them. They’d obviously thought that safety lay on the other side, and the young soldier found himself saddened almost to tears as he imagined the last desperate moments of their lives; a sadness that turned to soul racking pity when he saw he bodies of two young children who’d been dragged here by their father in a vain attempt to save them.

     All the doors except one had red flags in their windows, and Matthew realised that their twin doors beyond must have been open when the calamity struck. The fifth door was open, though, and the alcove between it and its twin was packed with at least a dozen corpses, including children in the arms of their parents. If they’d been able to close the door behind them they’d have been able to open its twin, which had a red flag in its window, but he guessed that every attempt to do so had been thwarted by the press of more people desperate to get in. These poor wretches hadn't been killed in the same way as the others, the young soldier realised. These people had been killed by panic.

     Steeling himself for the gruesome ordeal, Matthew went through the door and gently eased his way through the corpses to the second door. Looking through the window, he saw that all five sets of double steel doors opened into a fifteen foot wide corridor leading away from him, a corridor that had smaller corridors branching off it on either side and that seemed to open out, a hundred yards away, into another large cavern. The place was huge! he realised, but the thing that really surprised him, surprised him so much that he almost fell backwards among the mummified corpses, was that there were people walking along those corridors! Living people!

     They were dressed as though they were going to a historical fancy dress party, in a style that had been popular in the last days of the Agglemonian Empire. The women wore long, flowing robes of white, yellow and blue that hung down to their ankles but left their arms bare. They all wore their hair up in a beehive, tied with ribbons and ornamental hairpins, except for the younger girls who wore their hair loose, in some cases reaching all the way down to their waists. The men, on the other hand, all had their hair cut very short. They were almost bare chested, wearing only skimpy tunics open at the front, and they wore short skirts that exposed their hairy legs. The only people dressed differently were a pair of soldiers who appeared from a corridor on Matthew’s left. He watched as they crossed the corridor street at a leisurely pace, chatting as they went, disappearing from sight down a corridor to his right. Their breastplates, helmets and swords were similar to the pictures he’d seen of Agglemonian soldiers in old history books. They were also the only people he’d seen so far who wore anything on their feet; tough looking leather boots, great for marching for miles through rough countryside but completely superfluous in an indoor, underground environment and obviously worn only to complete the uniform.

     “Agglemonians!” gasped Matthew in astonishment. “Real, actual, living Agglemonians! But how? How is it possible?” At that moment, a young man looked in his direction and he ducked down, suddenly afraid he’d been seen looking through the window. Suddenly he felt very alone and very vulnerable, and he imagined dozens of them becoming aware of his presence, being angry at him for spying on them and coming through the door to get him. In fact, he was perfectly safe. There was absolutely no way they could reach him even if they’d known he was there and if he’d thought about it for a while he would have realised it, but intelligent though he was he lacked Thomas’s natural genius and was incapable of making the cognitive leap that would have revealed the truth. All he knew was that he was all alone, and that an unknown number of possibly dangerous strangers were just a few feet away on the other side of the door.

     “To Hell with this!” he told himself, squeezing his way back through the crumbling corpses and back into the park cavern. “High time I was getting back!” So saying, he began to retrace his steps.

     Now that he know how the steel doors worked, it took him only a few moments to leave the cavern and get back into the alcove through which he'd entered. The only difference was that, whereas before the hissing noise that accompanied the raising and lowering of the red flags had been accompanied by a terrible suction through the small hole in the door, this time it was accompanied by a powerful draught blowing in through an identical hole in the other door, a draught that blew all the dust on the ground into a billowing cloud that got into his eyes, making them water painfully.

     As the hissing and the wind stopped and the dust settled, he remembered the signs he’d seen of a gale that seemed to have blown around the park cavern at the same time that everyone in it had died, and for a moment he came very, very close to making the connection and understanding what had happened. His mind didn’t quite have what it took, though, and it slipped away from him before he even knew it had been there. He just stood there in momentary puzzlement, sensing he was close to something but not knowing what, before shaking his head dismissively and opening the door.

     Back in the corridor, he was delighted to find that sound had returned, and all the way back to the top of the spiral staircase he was aware as he’d never been before of the rustling his clothes made as he walked and the sound of his boots on the hard, dusty ground. Near the top of the staircase, though, as he paused to rest and allow his pounding heart to settle down, he remembered the necklace he was wearing and took it off. He gazed adoringly at the huge diamond one last time, then stuffed it into his pocket, intending to bury it deep down in his backpack as soon as he got back to where he'd left it. Then he took a deep breath and continued on to the top of the stairs.