The Revelation Space Collection (431 page)

‘Trust me,’ Celestine said. ‘It’s perfectly safe to enter.’

This time the markings looked more complicated, and at first I feared that Celestine had been over-confident.

On the left-hand side of the door - extending the height of the frame - was a vertical strip marked by many equally spaced horizontal grooves, in the manner of a ruler. But some of the cleanly cut grooves were deeper than the others. On the other side of the door was a similar ruler, but with a different arrangement of deeper grooves, not lining up with any of those on the right.

I stared at the frame for several seconds, thinking the solution would click into my mind; willing myself back into the problem-solving mode that had once seemed so natural. But the pattern of grooves refused to snap into any neat mathematical order.

I looked at Childe, seeing no greater comprehension in his face.

‘Don’t you see it?’ Celestine said.

‘Not quite,’ I said.

‘There are ninety-one grooves, Richard.’ She spoke with the tone of a teacher who had begun to lose patience with a tardy pupil. ‘Now counting from the bottom, the following grooves are deeper than the rest: the third, the sixth, the tenth, the fifteenth . . . shall I continue?’

‘I think you’d better,’ Childe said.

‘There are seven other deep grooves, concluding with the ninety-first. You must see it now, surely. Think geometrically.’

‘I am,’ I said testily.

‘Tell us, Celestine,’ Childe said, between what was obviously gritted teeth.

She sighed. ‘They’re triangular numbers.’

‘Fine,’ Childe said. ‘But I’m not sure I know what a triangular number is.’

Celestine glanced at the ceiling for a moment, as if seeking inspiration. ‘Look. Think of a dot, will you?’

‘I’m thinking,’ Childe said.

‘Now surround that dot by six neighbours, all the same distance from each other. Got that?’

‘Yes.’

‘Now keep on adding dots, extending out in all directions, as far as you can imagine - each dot having six neighbours.’

‘With you so far.’

‘You should have something resembling a Chinese chequerboard. Now concentrate on a single dot again, near the middle. Draw a line from it to one of its six neighbours, and then another line to one of the two dots either side of the neighbour you just chose. Then join the two neighbouring dots. What have you a got?’

‘An equilateral triangle.’

‘Good. That’s three taken care of. Now imagine that the triangle’s sides are twice as long. How many dots are connected together now?’

Childe answered after only a slight hesitation, ‘Six. I think.’

‘Yes.’ Celestine turned to me. ‘Are you following, Richard?’

‘More or less . . .’ I said, trying to hold the shapes in my head.

‘Then we’ll continue. If we triple the size of the triangle, we link together nine dots along the sides, with an additional dot in the middle. That’s ten. Continue - with a quadruple-sized triangle - and we hit fifteen.’ She paused, giving us time to catch up. ‘There are eight more; up to ninety-one, which has thirteen dots along each side.’

‘The final groove,’ I said, accepting for myself that whatever this problem was, Celestine had definitely understood it.

‘But there are only seven deep grooves in that interval,’ she continued. ‘That means all we have to do is identify the groove on the right which corresponds to the missing triangular number.’

‘All?’ Hirz said.

‘Look, it’s simple. I know the answer, but you don’t have to take my word for it. The triangles follow a simple sequence. If there are N dots in the lower row of the last triangle, the next one will have N plus one more. Add one to two and you’ve got three. Add one to two to three, and you’ve got six. One to two to three to four, and you’ve got ten. Then fifteen, then twenty-one . . .’ Celestine paused. ‘Look, it’s senseless taking my word for it. Graph up a chequerboard display on your suits - Forqueray, can you oblige? - and start arranging dots in triangular patterns.’

We did. It took quarter of an hour, but after that time we had all - Hirz included - convinced ourselves by brute force that Celestine was right. The only missing pattern was for the fifty-five-dot case, which happened to coincide with one of the deep grooves on the right side of the door.

It was obvious, then. That was the one to press.

‘I don’t like it,’ Hirz said. ‘I see it now . . . but I didn’t see it until it was pointed out to me. What if there’s another pattern none of us are seeing?’

Celestine looked at her coldly. ‘There isn’t.’

‘Look, there’s no point arguing,’ Childe said. ‘Celestine saw it first, but we always knew she would. Don’t feel bad about it, Hirz. You’re not here for your mathematical prowess. Nor’s Trintignant, nor’s Forqueray.’

‘Yeah, well remind me when I can do something useful,’ Hirz said.

Then she pushed forward and pressed the groove on the right side of the door.

Progress was smooth and steady for the next five chambers. The problems to be solved grew harder, but after consultation the solution was never so esoteric that we could not all agree on it. As the complexity of the tasks increased, so did the area taken up by the frames, but other than that there was no change in the basic nature of the challenges. We were never forced to proceed more quickly than we chose, and the Spire always provided a clear route back to the exit every time a doorway had been traversed. The door immediately behind us would seal only once we had all entered the room where the current problem lay, which meant that we were able to assess any given problem before committing ourselves to its solution. To convince ourselves that we were indeed able to leave, we had Hirz go back the way we had come in. She was able to return to the first room unimpeded - the rear-facing doors opened and closed in sequence to allow her to pass - and then make her way back to the rest of us by using the entry codes we had already discovered.

But something she said upon her return disturbed us.

‘I’m not sure if it’s my imagination or not . . .’

‘What?’ Childe snapped.

‘I think the doorways are getting narrower. And lower. There was definitely more headroom at the start than there is now. I guess we didn’t notice when we took so long to move from room to room.’

‘That doesn’t make much sense,’ Celestine said.

‘As I said, maybe I imagined it.’

But we all knew she had done no such thing. The last two times I had stepped across a door’s threshold my suit had bumped against the frame. I had thought nothing of it at the time - putting it down to carelessness - but that had evidently been wishful thinking.

‘I wondered about the doors already,’ I said. ‘Doesn’t it seem a little convenient that the first one we met was just the right size for us? It could have come from a human building.’

‘Then why are they getting smaller?’ Childe asked.

‘I don’t know. But I think Hirz is right. And it does worry me.’

‘Me too. But it’ll be a long time before it becomes a problem.’ Childe turned to the Ultra. ‘Forqueray - do the honours, will you?’

I turned and looked at the chamber ahead of us. The door was open now, but none of us had yet stepped across the threshold. As always, we waited for Forqueray to send his float-cam snooping ahead of us, establishing that the room contained no glaring pitfalls.

Forqueray tossed the float-cam through the open door.

We saw the usual red stutters as it swept the room in visible light. ‘No surprises,’ Forqueray said, in the usual slightly absent tone he adopted when reporting the cam’s findings. ‘Empty metallic chamber . . . only slightly smaller than the one we’re standing in now. A door at the far end with a frame that extends half a metre out on either side. Complex inscriptions this time, Celestine.’

‘I’ll cope, don’t you worry.’

Forqueray stepped a little closer to the door, one arm raised with his palm open. His expression remained calm as he waited for the drone to return to its master. We all watched, and then - as the moment elongated into seconds - began to suspect that something was wrong.

The room beyond was utterly dark; no stammering flashes now.

‘The cam—’ Forqueray said.

Childe’s gaze snapped to the Ultra’s face. ‘Yes?’

‘It isn’t transmitting any more. I can’t detect it.’

‘That isn’t possible.’

‘I’m telling you.’ The Ultra looked at us, his fear not well concealed. ‘It’s gone.’

Childe moved into the darkness, through the frame.

Just as I was admiring his bravery I felt the floor shudder. Out of the corner of my eye I saw a flicker of rapid motion, like an eyelid closing.

The rear door - the one that led out of the chamber in which we were standing - had just slammed shut.

Celestine fell forward. She had been standing in the gap.

‘No . . .’ she said, hitting the ground with a detectable thump.

‘Childe!’ I shouted, unnecessarily. ‘Stay where you are - something just happened.’

‘What?’

‘The door behind us closed on Celestine. She’s been injured . . .’

I was fearing the worst - that the door might have snipped off an arm or a leg as it closed - but it was, mercifully, not that serious. The door had damaged the thigh of her suit, grazing an inch of its armour away as it closed, but Celestine herself had not been injured. The damaged part was still airtight, and the suit’s mobility and critical systems remained unimpaired.

Already, in fact, the self-healing mechanisms were coming into play, repairing the wound.

She sat up on the ground. ‘I’m OK. The impact was hard, but I don’t think I’ve done any permanent damage.’

‘You sure?’ I said, offering her a hand.

‘Perfectly sure,’ she said, standing up without my assistance.

‘You were lucky,’ Trintignant said. ‘You were only partly blocking the door. Had that not been the case, I suspect your injuries would have been more interesting.’

‘What happened?’ Hirz asked.

‘Childe must have triggered it,’ Forqueray said. ‘As soon as he stepped into the other room, it closed the rear door.’ The Ultra stepped closer to the aperture. ‘What happened to my float-cam, Childe?’

‘I don’t know. It just isn’t here. There isn’t even a trace of debris, and there’s no sign of anything that could have destroyed it.’

The silence that followed was broken by Trintignant’s piping tones. ‘I believe this makes a queer kind of sense.’

‘You do, do you?’ I said.

‘Yes, my dear fellow. It is my suspicion that the Spire has been tolerating the drone until now - lulling us, if you will, into a false sense of security. Yet now the Spire has decreed that we must discard that particular mental crutch. It will no longer permit us to gain any knowledge of the contents of a room until one of us steps into it. And at that moment it will prevent any of us leaving until we have solved that problem.’

‘You mean it’s changing the rules as it goes along?’ Hirz asked.

The Doctor turned his exquisite silver mask towards her. ‘Which rules did you have in mind, Hirz?’

‘Don’t fuck with me, Doc. You know what I mean.’

Trintignant touched a finger to the chin of his helmet. ‘I confess I do not. Unless it is your contention that the Spire has at some point agreed to bind by a set of strictures, which I would ardently suggest is far from the case.’

‘No,’ I said. ‘Hirz is right, in one way. There have been rules. It’s clear that it won’t tolerate us inflicting physical harm against it. And it won’t allow us to enter a room until we’ve all stepped into the preceding one. I think those are pretty fundamental rules.’

‘Then what about the drone, and the door?’ asked Childe.

‘It’s like Trintignant said. It tolerated us playing outside the rules until now, but we shouldn’t have assumed that was always going to be the case.’

Hirz nodded. ‘Great. What else is it tolerating now?’

‘I don’t know.’ I managed a thin smile. ‘I suppose the only way to find out is to keep going.’

We passed through another eight rooms, taking between one and two hours to solve each.

There had been a couple of occasions when we had debated whether to continue, with Hirz usually the least keen of us, but so far the problems had not been insurmountably difficult. And we were making a kind of progress. Mostly the rooms were blank, but every now and then there was a narrow, trellised window, panelled in stained sheets of what was obviously a substance very much more resilient than glass or even diamond. Sometimes these windows opened only into gloomy interior spaces, but on one occasion we were able to look outside, able to sense some of the height we had attained. Forqueray, who had had been monitoring our journey with an inertial compass and gravitometer, confirmed that we had ascended at least fifteen vertical metres since the first chamber. That almost sounded impressive, until one considered the several hundred metres of Spire that undoubtedly lay above us. Another few hundred rooms, each posing a challenge more testing than the last?