It was a small room, barely six feet by ten, and the five of them had a tight squeeze getting into the tiny area of floor that wasn’t covered by desks, cabinets, a large table and a single high backed chair. Whereas every other item of furniture they’d seen so far in the complex had been bare and empty, though, these ones were covered by great piles of books, ledgers, folders and loose sheets of paper, some stacked neatly but the great majority heaped in chaotic disarray all over every horizontal surface.

     Thomas picked up the topmost sheet of paper, blew the dust off and tried to read it, not easy since the ink had faded almost to invisibility during the centuries since it had been written. “The Empire is falling,” he read, “and many of the great seats of lore, wisdom and knowledge have already been destroyed, the priceless treasures they contained burned like garbage by the new barbarians. I am determined that the same fate shall not befall my own life’s work, or that of my predecessors, and so I have brought all our notes and records, all our theories and speculations, and my entire personal library up here to this timeless moon where, the Gods willing, they will survive the coming dark age and be found by men of learning and wisdom when civilization rises again, as I am confident it will. May Tizar, the source and guardian of all wisdom, watch over this priceless hoard and keep it safe down through the centuries. It’s signed Pottrik Marr, the last Astronomer Imperial.”

     “Priceless hoard?” said Shaun doubtfully, looking around the dusty room.

     “Yes!” exclaimed Thomas emphatically. “It’s obvious when you think of it! Those lenses don’t have to just look down on Tharia, they could just as easily look up at the stars and the other planets. The Emperor must have allowed one or two of the lenses to be used by astronomers, and it’s all up here, two thousand years of astronomical observations. You don’t get much more priceless than that!”

     He picked up a big, thick book and opened it to see every page covered by drawings of Lamon, the next planet in towards the yellow sun, with various changing features such as clouds and dust storms labelled in fading ink. It was labelled ‘Lamon 1152 - 1185’, and looking around he saw dozens of other volumes, each containing twenty or thirty years worth of observations of the same planet. Nearby, other bookshelves contained a similar number of volumes dedicated to the other planets.

     “You’d think they’d get fed up drawing the same thing over and over again for so long,” said Jerry, rather unimpressed. “What’s the point? You draw them once, what’s the point of drawing them again?”

     Good point, thought Thomas. He took two volumes of drawings of Lamon, one from the early days of the Empire and the other from near its end. He opened them both to compare them. “Look!” he exclaimed in excitement. “They’re different. See how those dark areas are small and patchy in this one, but here, in the drawing done nearly a thousand years later, they’ve grown to cover almost the entire hemisphere.”

     “That’s because they were drawn by different artists,” replied the tiny nome. “The second one was probably done with a darker pencil and a heavier hand. Besides, how do you know both drawings are of the same part of the planet?”

     “They’re marked in longitude and latitude,” replied Thomas, showing him. “That’s why they kept observing and drawing for so long, to see how the planets change down through the centuries.”

     “Ah, here you are,” said Matthew, entering behind the others. “I wondered where you’d gone.”

     “Are the trogs okay?” asked Diana.

     “Yeah, they’re fine. They reckon they’ll be through in another couple of hours.”

     “Did you tell them what we found up here?” asked Shaun.

     “No,” said Matthew, grinning. “I told them to come get us when they get through. I can’t wait to see the looks on their faces when they see the world through that window!”

     The others all grinned at the thought, then filed back out to return to the observation room, leaving Thomas all alone. The wizard barely noticed they’d gone as he pulled out another book, a look of sheer bliss on his face. This was Thomas’s idea of paradise. Being surrounded by the accumulated wisdom of centuries and being left alone to read it in peace, and as he discovered that the book contained words rather than pictures, being a summary of everything that was known about the planet Sereena, he could almost imagine that he’d died and gone to heaven.

     He read blissfully for a few minutes, before gradually becoming aware of a wonderful fragrance coming from somewhere behind him. A sweet, fresh smell so indescribably wonderful that he looked around to see what it was, and almost bumped his head against Lirenna’s, who’d been reading over his shoulder and inadvertently breathing almost directly into his face.

     “Oh, sorry,” he stammered in embarrassment, “I didn’t see you there. I thought you’d gone with the others.”

     “I did, but I came back,” replied the demi shae. She reached across him to pick up another book, a much thinner one filled with columns of numbers. “Guest stars,” she read on the cover. “What are they?”

     “A star that suddenly appears where there wasn’t one before,” replied Thomas. “They shine for a few days, weeks or months and then fade out again. Some are so bright they can be seen in the daytime.”

     “Really? Where do they come from?”

     “No-one knows. Some sages say that they’re ordinary stars that are so far away that they’re too dim to see, but which suddenly become brighter for some reason. If that’s true, imagine if it happened to a star that was already bright. It would be like having a third sun!”

     Lirenna’s eyes widened in fascination, but the columns of numbers failed to hold her interest for long and she picked up another book. “Variations in the diameter of Derro,” she read. It was also filled with columns of numbers, but on the first page was a folded graph three feet long on which they’d been plotted, diameter against time. Their University education had included a very brief series of lectures on the basic principles of mathematics, so that she was able to read the graph.

     “Tom, look at this,” she said after a few minutes, and because of the strange tone in her voice he put down the book he’d been reading to look. The graph consisted of a wavy line that went up and down with about fifty years between one peak and the next, but it also had a slight, general downward slope so that the end of the graph was noticeably lower than the start, a thousand years earlier.

     “By the Gods!” he exclaimed. “So Derro’s getting smaller, is it? But very, very slowly, over centuries.” He stared off into the distance for a few moments, deep in thought. “So if you extrapolate that graph back into the past, you’d see Derro getting larger and larger until, tens of thousands of years ago, it would have been enormous. Lenny, do you remember that time when we were in the Ghost Ocean?”

     The demi shae shuddered. She remembered all too well. “What about it?” she asked.

     “We saw an image of the world as it was two or three million years ago,” said Thomas, “but do you remember, we couldn’t see the image of the red sun of the past. Strange, don’t you think?”

     “I think it’s dangerous to extrapolate too far into the past,” warned the demi shae. “We’re talking about hundreds of years here, not millions.”

     “Yes, yes of course,” agreed Thomas. “Still, I wonder how long it’ll go on shrinking for? Will it go on shrinking forever?”

     “Who knows?” sighed Lirenna, sorry she’d brought it up. “It’s probably not shrinking at all, just getting further away.”

     Thomas sat as if stunned. “Lenny, that’s brilliant!” he exclaimed. “Why didn’t I think of that? It’s so obvious, it’s distance, not size! That’s why it wasn’t visible two million years ago. It existed all right, but it was too far away too see. It came closest a few thousand years ago, and now it’s going away again, or we’re going away from it. I wonder how big it looked when it was closest?”

     “Why is the line wavy, though?” asked Lirenna, looking back at the graph. “It goes up and down every fifty years, as if...”

     “As if Derro were beating like a monstrous heart,” said Thomas dreamily, “taking fifty years for each beat. It even looks the colour of blood!”

     At that moment, Shaun popped his head around the door. “Er, could you give us a hand with something please, Tom?”

     “What is it?” asked the wizard, putting the book down reluctantly.

     “The door to the teleportation cubicle’s stuck. Could you give us a hand getting it open?”

     “Stuck?” asked Lirenna as they followed him out.

     “Di wanted to go back and see how the trogs’re getting on, but she couldn’t get the door open. It’s probably just stuck, three hundred years without any oil on its hinges. If we all give it a good tug at once, it’ll probably open.”

     “It’d better,” said Thomas, hurrying now. “Fascinating though this place is, the thought of spending the rest of my life here doesn’t exactly appeal.”

     They reached the large central room containing the teleportation cubicle to find Matthew, Jerry and Diana gathered around it, all pulling hard on the handle to no avail. Jerry backed away as they arrived and Shaun and Thomas took his place, there being just room for four to hold the handle at once. “Okay, all together now,” said the soldier. “As hard as you can. Pull!”

     They all pulled, but the door didn’t budge. “Again!” said Shaun and they all pulled even harder, but with no more success than before. “Again!” cried Shaun, and again and again, but the door remained stubbornly closed, not moving by even the tiniest amount, and the four of them let go to rest their tired arms.

     “It’s no good,” puffed Thomas, sweating partly from the exertion but mostly from fear. “That door’s not stuck, it’s locked.”

     “Locked!” exclaimed Diana in alarm. “But how?”

     “Who was the last one through?” asked the wizard.

     They all looked at Matthew. “Don’t look at me!” he protested indignantly. “I didn’t do it!”

     “Did you do anything different when you came back?” demanded Shaun. “Did you touch anything, move anything?”

     “No!” replied Matthew angrily. “I didn’t do anything!”

     “Most probably it locked itself,” said Thomas. “There’s no obvious mechanical lock, so it’s probably magically locked, but spells like that can fade over very long periods of time, which is how we were able to get in. When we started going in and out, though, we jogged it back into life. Give it time and it’ll probably fade again.”

     “How long?” asked Shaun hopefully.

     “No way of knowing,” replied Thomas. “Five minutes, five years...”

     “What!”

     “All right, calm down,” said Diana soothingly. “Let’s not get over excited. First of all, the trogs are still down there, and the door may open from their side. And secondly if this door’s locked, there ought to be a way to unlock it. How do you unlock magically locked doors, Tom?”

     “Well, there is a spell designed for that very purpose,” replied the wizard, “but unfortunately I don’t know it.” He looked hopefully at Jerry and Lirenna, but they both shook their heads as well.

     “We’ll break it down,” said Matthew. “Smash the door in!”

     “No!” cried Thomas in alarm. “If you do that, we’ll never get out! These teleportation cubicles are activated by closing the door behind you, and you can’t do that if the door’s busted.”

     “All right, so what in the name of Hell are we going to do?” asked Shaun in frustration.

     “How should I know?” cried back Thomas, now beginning to feel genuinely afraid. The installation they were in was larger than the steel box they’d found themselves in after leaving the Underworld, but the situation was the same and the nightmare of a slow, lingering death was beginning to raise its ugly head again. Diana and Lirenna glanced at each other, their faces growing pale as the truth of the situation gradually dawned on them as well.

     “Hey,” said Jerry suddenly, examining some markings on the door, about half way up its left side. “I think this is a Garnissian door. What do you think, Tom?”

     Thomas and Lirenna stepped closer to examine the markings. “What’s a Garnissian door?” asked Diana hopefully. “Is that good?”

     “Could be,” replied Lirenna. “I think you’re right, Jerry. It’s got all the signs.”

     “Yeah,” agreed Thomas. “This would be the activation point.”

     “What’s a Garnissian door?” repeated Shaun, louder.

     “It’s a special kind of magically locked door invented by a wizard called Garnis,” replied Jerry. “It’s locked and unlocked by a magic key, so all we’ve got to do is find the key and we’re out of here.”

     “The bad news,” added Thomas, “is that without the key, there’s no other way of opening the door from either side, so the trogs won’t be coming to rescue us. Unless the locking spells fade again, of course.”

     Shaun gave the door a tug, just in case, but it was still firmly locked. “Okay,” he said, “so where’s the key?”

     “I’m afraid that’s the other bad news,” said Thomas, looking meaningfully around the bare room. “I’m afraid that the Agglemonians almost certainly took it with them when they left.”

     It took a few seconds for the full impact of Thomas’s words to sink in, but when they did the soldier’s eyes widened in horror. “That’s great!” he cried, sheer terror beginning to creep into his voice. “That’s just bloody great! So what in the name of hell are we going to do now?”