*There's a little more to it,' the golem said. Eunice was leading them down an ice-walled tunnel. It had been bored roughly, then fixed with spray-on sealant. A walkway had been fastened to the floor, handrails and grabs to the walls, lights to the ceiling. The air was turning cold again. *Mercury was a double-blind. The artilect research was genuine, but that wasn't the sole point of our being there. The basic physics research wasn't just a screen. It was as equally valid a if not more important.' She was skimming the tunnel in long, loping strides a human locomotion, not the limb-over-limb tumble that the golem had demonstrated earlier. And looking back, smiling with uncontained pleasure. It was the delight of someone who hadn't had an audience in a very long while. She was enjoying the showmanship, her moment in the spotlight. *On Mercury, we tested a hypothesis. We constructed a relatively small-scale experimental physics facility to probe certain obscure byways of high-energy quark-quark interactions. There were bigger physics labs elsewhere a in Earth orbit, on the Moon a but we needed discretion. Above all, we had energy in abundance.'

*What did you find?' Geoffrey asked.

*What appeared to be an unpromising little side-avenue . . . that turned out to lead to something astonishing. Utterly unsuspected, utterly unexplored. We'd broken through into an entire garden of new physics. We were breaching unification energies almost without trying. Seeing exotic-matter by-products that shouldn't have been created since the universe was more than a couple of Planck-lengths wide.' Eunice shook her head in amazement. *The wonder was that we didn't blow ourselves off Mercury. We came close, in the early days. Then we dialled it back a bit and became cautious. Very cautious. It was clear that the physics we were investigating needed a bigger experimental facility.'

*You say "we",' Geoffrey said. *Who else was in on this? You can't keep that kind of thing secret if more than a handful of people are involved.'

*Only a handful were,' Eunice said. *With artilects and robots handling the complex construction and analysis tasks, it was easy enough to run the physics facility with just a skeleton crew a and most of them thought they were working on minor refinements to propulsion design. As to who knew the full story, there were just two of us.'

*You were never a physicist,' Geoffrey said.

*I didn't say I was.'

They'd reached the end of the ice-walled tunnel. The door here was as heavy and sturdily armoured as a surface airlock, fixed inside a frame that was obviously well braced into the surrounding ice. It opened for the golem, and she led Geoffrey and Jumai through it.

Inside was a small control room a just a couple of consoles and buckle-in seats facing three large triangular-framed windows screened with heavy-duty slats. The wall behind them, flanking either side of the door, was lined with grey lockers and equipment racks. There was some kind of decorative sculpture on the wall to Geoffrey's right, while the one to his left was occupied by a single large display which appeared to show Lionheart and its environs at a variety of logarithmic scales, culminating in one that was big enough to encompass the iceteroid's orbit around the sun. Geoffrey's eyes tracked to the smaller orbits of the outer gas giants; then inwards to the still smaller paths of Saturn and Jupiter. Mars, Earth, Venus and Mercury fell into an area he could easily have covered with the palm of his hand.

They were a long way out. Every now and again something would remind him of that, and the feeling was like vertigo. How could his grandmother ever willingly have sought this isolation, this sense of immense displacement from home?

*It's a shame your sister isn't here,' Eunice said. *I'd have liked her to see this.'

*This' was the sculpture, on the wall to his right. It was a slightly irregular rectangle, about the size of a Persian rug, fixed vertically against the wall. The rectangle was in fact a mosaic of smaller pieces a black shapes, mostly about the size of his hand, which, to judge by their jagged outlines, must once have fitted together to form a single whole. Now there were gaps and fissures where they didn't quite join. There were also entire pieces missing from the edges and the middle a bites and absences where the grey backing of the wall showed through.

For all that their edges were irregular, the surfaces of the pieces a the visible faces a were as smooth as if they'd been chiselled along fracture lines. Aside from the occasional chipped or cratered piece, the dark mosaic was uniform in thickness. It gleamed with a magpie lustre, blues and greens shimmering back at Geoffrey, and within the shimmer the suggestion of faint intersecting scratches. Studying the scratches more intently, he made out what could almost have been totemic figures in cave art a a dance of headless, splayed-limb psychopomps made up of dashes and squiggles and spirals.

*Would Sunday have recognised this?' He wondered, momentarily, whether it might actually be his sister's work, but he didn't think so. With solid forms, her work tended towards the figurative. When she worked with abstract compositions, she employed every colour in the paintbox.

*That would depend,' Eunice said. She had positioned herself at one of the consoles and now opened the shutters covering the main windows. They whisked away with a series of loud clunks, leaving only glass between the control room and what was obviously a very large vacuum-filled cavity inside the iceteroid. *That shielding was never going to make much difference if one of the reactions went critical,' Eunice remarked, *but it made me feel marginally safer knowing it was in place.'

They might have been looking at the interior of the drilling operation, spotlit for visitors. The cavity was impressively large a an easy kilometre across, stretching away to the left and right around a great curve so that the far ends were not visible from their vantage point. If in fact there were ends at all, for, Geoffrey decided, it was just as likely that the cavity was toroidal, a doughnut-shaped hole dug out of the middle of Lionheart. Bolstering that suspicion was the fact that a metal tube came around the bend of the cavity, passed by the observation point and continued on its arcing trajectory around the other end. The tube was fixed to the inner walls of the cavity by cartwheel-shaped assemblies, each shock-absorbing spoke as thick as a railway carriage. The tube itself was as wide as a major thoroughfare. Like a sated python, it bulged here and there, and secondary pipes branched out from it at various angles, plunging into the cavity wall.

*A lot of metal,' Geoffrey said.

*Twenty million tonnes,' Eunice said, with a touch of pride. *All of it shipped up from the main belt under the pretence that it was for normal mining operations. Would have been impossible if we didn't already have a massive system-wide manufacturing and transportation network in place. A few thousand tonnes diverted from this facility, a few more from that . . . over time, it added up. But books still had to be cooked. One thing to keep a commercial secret from our competitors; another to run a secret project within the family. It took ten years, and there were many occasions when it nearly came undone. I couldn't have done it without help a someone to cover my tracks, make sure there were no loose ends in the administration.'

*So that's two people who knew, other than yourself,' Jumai said.

Eunice smiled tersely. *I made the initial discovery. But a as Geoffrey so kindly pointed out a I'm no physicist. Never was. I could be guided into a kind of understanding, but it was never more than a shallow approximation of the real thing.'

Geoffrey asked, *How could you make a discovery, without being a physicist?'

*By luck. Luck and the wit to know that what I'd found might be useful, and that I should speak to someone who might be better informed than me.' She touched a control and the shutters slammed back into place with the sound of a dozen rivet-guns firing simultaneously. *The experiment's powered down now,' she said, *but it still gives me the flutters, seeing that thing out there.'

*You needed the solar grid on Mercury to run the first experiment,' Jumai said. *Sun's colder than a witch's tit out here. How did you find the energy?'

Eunice laughed a not because it was a stupid question, Geoffrey decided, but rather one she liked. *That's simple. I ran the second experiment off a small reactor derived from the first.'

She moved to the black tableau on the right-hand wall and detached one of the fist-sized fragments. It came off easily, leaving no trace of a hook or adhesive.

*A piece of Chakra's Folly,' she said, tossing the item to Geoffrey. In Lionheart's low gravity, he had ample time to catch it. *The Phobos Monolith. Your sister would have seen it, I think a on her way to the Indian settlement where I spent some time before descending to Mars.'

Geoffrey caressed the black fragment, convinced that he'd already handled it. *This is a piece of Phobos?'

*Something that ended up there. People have known about the Monolith for at least a hundred and fifty years a they saw the shadow it cast long before they got a good close-up look at the thing itself. For a while, there were cranks who thought it might be an alien artefact a a ship, a sentinel, something like that. But when we got there we found that it was exactly what all reasonable people had always expected: a very big boulder, jammed into Phobos like a splinter. Impressive, hard to miss a a viable tourist attraction. But not an alien machine.'

*Then why am I holding this?'

*I wasn't the first to see it up close. Not even the fiftieth. By the time I got there, nearly a hundred people had already come through Phobos on their way to Mars a I was the ninety-eighth. And countless robot eyes had already scanned and photographed the Monolith. They'd seen it for what it was: a clearly natural feature, the result of some ancient collisional process.' Eunice waited a breath, then added, *But they'd all missed something.'

*Something you didn't,' Jumai said.

*I found debris,' Eunice said, *near the base of the Monolith, loosely scattered over the Phobos surface material a bound there only weakly, due to the low gravity. That thing had been sticking up from the crust like a target in a shooting gallery for countless millions of years. Eventually something had hit it, some speck of cosmic dirt, and chipped off an entire face. I was looking at the debris, the shards of that high-velocity impact. Others must have realised what had happened, I suppose. But it had never occurred to any of them to pay attention to the debris.'

Geoffrey was still studying the piece in his hand. *You realised there was more to it than just debris.'

*You can't have missed those fine surface markings. On the face of it, they could be anything: spallation tracks from cosmic rays, crystalline defects . . . but something about them held my eye. I picked up another piece, lying close by. Then another. Eventually a and my suit air was running low by then a I found a matching pair. I fitted them together and saw that the scratches connected, and that they appeared to form part of some larger . . . diagram.'

*I'd laugh if there was any possibility you might be joking,' Geoffrey said.

*I went back out there many times over the following weeks. I gathered as many of the fallen shards as I could find, bringing them back to the encampment. It was easy enough to keep the pieces hidden in my personal effects, and since we were going into a gravity well, not crawling out of one, there was no mass restriction for the trip down to Mars.'

*Did Jonathan know?' Geoffrey asked.

*I saw no reason to keep it from him. He was my husband, after all. And I didn't have any notion of what the scratches would actually turn out to symbolise. Obviously, their mere existence was astonishing. But beyond that . . . even if I went public, I couldn't see it being more than a seven-day wonder. So what if the scratches appeared to point to an alien presence on Phobos? It couldn't be proved, not rigorously. Someone could always claim that the shards had been faked by one of the first hundred. And if aliens had been there, a million or a billion years ago, they'd done nothing beyond leave that one set of scratches. Like someone stopping to take a piss at the roadside before carrying on.'

*Graffiti. Scratched on the Monolith,' Jumai said. *The kind of thing someone might do if they were stuck somewhere, bored, with nothing else to occupy them.'

*Jonathan had studied electrical engineering before making his fortune in telecomms,' Eunice said. *As part of his studies, he'd taken modules in modern physics. When I showed him the pieces, arranged as well as I was able, he said that the scratched forms reminded him of something. They look like little men, don't they, or demons?'

*That's what I thought,' Geoffrey said.

*To Jonathan they were reminiscent of Feynman diagrams: little conceptual drawings encoding the interaction histories of subatomic particles. They weren't Feynman diagrams, clearly a that would be as unlikely as finding inscriptions in our own alphabets or number systems. But they were analogous. The lines are the trajectories of particles. The squiggles are the forces mediating the reactions between them. The spirals are by-products of those reactions a other particles, packets of energy. That was just intuition, though. It would take a working physicist to say more than that. A good one, too. And someone I could trust.'

*And you just happened to know someone,' Jumai said.

*We established contact while I was on Mars,' Eunice answered. *He was fascinated by the rock drawings. He said that they already encoded the entire edifice of existing physics, as well as implying the correctness of several models that were still at the preliminary stage. What was more important, though, was that the diagrams pointed to physics we hadn't begun to probe. Quark-quark interactions that seemed forbidden, on the basis of the known gauge symmetries. Do you know much about quarks? No, obviously not, or you'd have realised that they come in three colours: blue, red and green, like cheap plastic jewels. Or that when Sunday finds me reading a copy of Finnegans Wake, there's a reason for that.'

*I don't think we did too badly to get this far,' Geoffrey said.

*The point was, if the diagrams were right . . .' Eunice shook her head, as if she was still experiencing the awe of that moment. *We could do incredible things. We could build engines powerful enough to fling a ship to Neptune in weeks. But that was just the start of it a the least dramatic breakthrough.' She smiled again. *My physicist was right, too. The engine that brought you to Lionheart was the fruit of that very early research. Really, it's just a standard VASIMR motor with a few wrinkles smoothed out. The kind of thing we'd probably have stumbled on eventually, given enough time. But this wasn't a stumble. We saw how to make it better, and it worked. You can't know how that made us feel. We'd proven that there was testable science in the rock diagrams. But if the least dramatic predictions gave us an engine five times faster than anything else out there, what would we be getting into when we started testing the really frightening predictions?'

*You tell us,' Geoffrey said.

*Even with the scope of the equipment in Lionheart, we could only probe the margins of the new physics. But that was enough, for now. These basic experiments have already pointed to a technology so potent that it would make the engine in that ship look like a toy.' Eunice gestured at the black mosaic. *We can do much better than that. For a hundred and fifty years we've been locked into a few hours of space around one little star. Even being able to reach Neptune in a few weeks doesn't alter that. But now we have the means to break out of the solar system. A stardrive, if you will. If the physics is to be believed, then true interstellar travel is now within our grasp. Let's be clear what we're talking about here. It's still going to take a long time. A few per cent of the speed of light, that's what we're looking at. Pitiful and inadequate compared to the scale of things. Horsepiss against all that cosmic immensity. Even the nearest solar system will still be hundreds of years away. But that's hundreds, not tens of thousands!'

She was becoming increasingly animated, as if this whole speech was approaching a carefully scripted climax.

*We already think on that kind of timescale, as a species. We're starting to live long enough, and we've accepted the burden of century-long endeavours like the repairing of Earth's climate. So it's not completely abhorrent to think of interstellar travel in those terms. Of course, there's a catch.'

*There'd have to be,' Geoffrey said, *or else why wouldn't you have gone public sixty years ago?'

She nodded, with what looked to Geoffrey to be inexpressible relief and gratitude, as if her most dire fear had been that he would not understand. *I said it wasn't a toy. Sixty years ago, I did not think that as a species we had the wisdom to accept these gifts. Not at the end of that century, when there were still people who not only remembered wars, but had experienced them . . . Would you have felt any more confident, in my shoes?'

Geoffrey discarded the flip answer he'd been about to give. *No,' he admitted. *Probably not.'

*The energy implicit in the rock diagrams would have been enough to wipe us out many times over,' Eunice said. *We'd dodged that bullet once, in the era of nuclear weapons. Did we have the collective smarts to dodge it a second time? I thought not a or at least had such grave doubts that I could not leave matters to chance. So I didn't. I followed what struck me as the only rational course, under the circumstances. I decided to sleep on matters, and see what happened.'

*You didn't sleep,' Geoffrey said. *You went into seclusion, for the next sixty-two years a or however long it was after you figured all this out. Then you died.'

*I didn't die,' Eunice said. *I just put other arrangements in place. Lin Wei and I might have had our differences, but I'd always hoped that Ocular would find something remarkable. When Lin came to me, when she presented the evidence of the Mandala structure on Sixty-One Virginis f, a series of processes were set in irrevocable motion. For the first time, we had a clear objective: a target for interstellar exploration. It felt right that we should also have the means to reach that target, if we so chose.'

*But you can't decide if the time is right,' Jumai said. *Maybe we're a fraction smarter than we were a hundred years ago, but is that smart enough? You're just an artilect. You can't possibly make that kind of choice.'

*I don't have to,' Eunice said. *I've merely passed on my responsibility. Now it's yours.'

*You're not serious,' Geoffrey said.

Eunice's smile was not without sympathy. *I did warn you that I was about to place a heavy burden on you.' She offered her hand, not for him to take, but to sweep majestically around the room. *All this is yours now. The experiment, the rock carvings . . . do with them as you will. If you think humanity deserves this gift, is ready for it . . . then it's yours to disseminate. Not as a commercial property, but as freely distributed knowledge. We're rich enough as it is, wouldn't you say? We can afford to give this away. If we're wise enough to deal with this as a species, then we're wise enough to deal with it collectively.'

*And if we don't think we're ready?' Jumai asked.

*Forget about what you've seen in Lionheart, or better still destroy it. You have the resources of the family at your disposal; shouldn't be too difficult.'

*Everyone's seen what the engine can do,' Geoffrey said. *Even if we wanted to keep this quiet, people will want to know how we did that.'

*Have the engine,' Eunice said dismissively. *Without the conceptual framework of the new physics, it's an awfully long leap from that to the stardrive.'

*Even that small advance changes everything,' Jumai said. *Just being able to get out here in a few weeks rather than months is going to shake things up. The outer solar system isn't going to look so far away any more.'

*So push the frontier back a little further,' Eunice said. *It's what I always did.' She clasped her hands. *Now, this may sound ungracious given that you've really only just arrived, but we should begin making preparations for your return journey. I was perfectly serious about not keeping you prisoner here. That wasn't the point of this exercise.'

*You'll let us take the ship back?' Jumai asked.

*After it's refuelled and repaired, which a with all of Lionheart turned to the task a shouldn't take more than a week. Then you can go back into hibernation. Perhaps when you arrive, you'll be closer to your decision.'

*I still don't know what happened to you,' Geoffrey said. *I know you didn't die in the Winter Palace because there was nobody up there to die, and consequently no ashes to be brought home, either. Which means that the last time anyone saw you alive a anyone we can trust, that is a was before you left for your final mission.'

*Lin Wei was kind enough to think of me,' Eunice said. *The least I can do is pay her back, in some small measure. Remember these numbers, and give them to Lin. I think they will answer at least one of your questions.' She reeled off a string of digits, then repeated them. *Lin Wei will understand.'

*There's one more thing,' Jumai said. *You talk as if you're the only person . . . the only thing . . . that knows any of this. Fine, you're an artilect a I'm ready to accept that there isn't another living soul in this iceteroid. But your husband knew, and you've told us about the physicist. You've also told us that it took insider help to pull all this off without the rest of your family finding out. So we're not the only ones, are we?'

*My husband died a long time ago,' Eunice said. *Long before the true significance of the rock drawings became clear. And anyway, even if he'd lived, and known . . . I'd still have trusted him to keep it all a secret. This information will be destabilising, whenever it's made public knowledge, and Jonathan liked stability more than anything else. That's why I left him on Mars.'

*And the physicist?' Geoffrey asked.

*He was a brilliant young Tanzanian,' Eunice said. *A brave and courageous thinker. But the rock drawings destroyed him. Not as a human being, but as a scientist. He'd . . . seen too much. Glimpsed too much of the inner workings of the universe, too soon and too quickly. He was a searcher after truth, and to have it revealed to him so readily, without effort . . . the entire intellectual purpose of his life was undermined in one blow. Once the experiments were designed, he pulled back a left the detailed running and interpretation to the artilects.'

*And the insider?' Geoffrey probed.

*The same person,' Eunice told him. *When he turned his back on physics . . . he returned to Africa. He was a very good man, and none of this could have been achieved without him.' Then her voice softened. *And now he has died, and you must go home to bury him.'

CHAPTER FORTY.

They were in Lionheart for a week, as the golem had anticipated. The ship was allowed to approach and dock, and soon after that robots were swarming all over it, attending to the damage and preparing it for the return journey home.

*We never had a name for it,' Geoffrey said, *since it obviously isn't the ship you left in.'

*Call it Summer Queen, if you like,' Eunice told them.

Since the repairs and refuelling were entirely automated processes, there was nothing Geoffrey and Jumai needed to do but wait until their ride was ready. They had been given the option of re-entering hibernation early, but both had decided against that. Neither wished to go to sleep until the ship was already on its way, putting distance between itself and the iceteroid.

Geoffrey couldn't speak for Jumai, but he had no difficulty analysing his own reluctance. He simply didn't have unquestioning confidence in Eunice, or in the artilect emulating her. It had already proven fallible, and for all that it articulated regret and sadness about Hector's death, and even Memphis's, he had no reason to suppose that those utterances carried the slightest emotional weight. It was making placating noises, but behind them, as Jumai had already pointed out, was just stuff. Machinery. And while machinery might ponder a set of actions that had led to a less than desirable outcome and adjust its future behaviour accordingly, it was a stretch to call that remorse.

Lionheart had been equipped to care for human visitors, and that was where they spent the week while Summer Queen a that name was as good as any a was overhauled. There was a suite of rooms and modules, a recreation complex, a gymnasium and a couple of centrifuges, one large enough to contain a commons and dining area a enough to keep a team of technical staff comfortable for months. They chose separate rooms and adjusted the furnishings accordingly to suit their preferences. There was entertainment, incoming transmissions a not full aug, but enough to keep them up to date on developments elsewhere in the system a and they had the means to send and receive private communications.

There was a limit to what Geoffrey was willing to discuss until he was face to face with his sister, but he told Sunday that they were both safe, and would be returning home as soon as the ship was cleared for departure. Allowing for the preparations, and the fifty-odd days of journey time it would take to reach near-Earth space, they would be back in two months.

*We'll be difficult to miss,' he said.

Then he called Lucas, and gave him the news about Hector.

Ten hours later, return transmissions arrived from Sunday and Lucas. Neither of them had a lot to say, simply expressing relief that Geoffrey and Jumai were alive, and would soon be on their way home. Lucas thanked Geoffrey for the news about his brother, but beyond that he was implacable, as if he wasn't entirely ready to take the news at face value. Even Sunday had appeared reticent to comment on it. She was in Africa, Geoffrey learned: after returning from Mars, she had travelled to the household to keep an eye on his elephants. Not just chinging, but physically there, in body and mind. He was grateful, and when he considered that by being in Africa she was necessarily neglecting her own life back on the Moon, her work and commissions, his gratitude became boundless. But Geoffrey and Jumai were coming back now, and Sunday didn't need to spend all that time waiting on Earth. He asked her to promise him that she would return to the Moon before his arrival.

Later, when Jumai and Geoffrey were dining in the centrifuge, being waited on by Plexus machines, she said, *They're not sure we're us. That's why they're holding back, I think. That and the fact that we're obviously holding back something as well. Can you blame them? We've been duped and manipulated by artilects; Sunday's been cheated by the Pans. Right now no one knows who or what to trust. For all they know, we might be dead by now.'

Geoffrey agreed. The fact that they couldn't give a plausible account of what had happened in Lionheart wasn't helping their case, either. It would be better when they got home, and he could talk properly. Not just with Sunday and Jitendra, but with Lucas as well. There was no escaping that. Lucas would have to be told about Lionheart.

*That's not really true,' Jumai said delicately. *Hector never got to find out why Eunice wanted us here.'

*So you're saying that because he was never let in on the secret, I don't have to share it with Lucas?'

*I'm saying you don't owe him anything. You didn't drag Hector into this a it was the other way around. Later, you saved his neck.'

*Didn't do him any good, did it? I just postponed it.'

*If Hector hadn't died . . . it would probably have been one of us. So consider that score settled. Did you hate him at the end?'

Geoffrey had to search himself for the honest answer. The automatic reply was to say that no, he had forgiven Hector everything. But the reality was more complicated than that. *We saw things differently,' he said, fingering the stem of his wine glass. *I believe there are absolutes. Rights and wrongs, lines in the sand. Moral certainties. I think Hector was wrong to go about things the way he did. He and Lucas shouldn't have blackmailed me, they shouldn't have used the elephants as a bargaining chip, and they shouldn't have put the family name above all other considerations.' He smiled at himself. *But I understand some of the cousins' fears now. More so than I ever have. I thought we might end up uncovering something, but I had no idea it was going to be this momentous. And Eunice was right: it is dangerous, and this knowledge shouldn't be shared until we're absolutely sure it won't rip humanity apart. Maybe we are ready for it, and maybe we're not a just yet. Either way, we know about it a you and me, and soon Sunday and Lucas. That means it's already out there, in a small way. And maybe Eunice was right about that but wrong about something else: that it'll take an enormous amount of luck for someone to go from Summer Queen to the physics behind the stardrive. If she's wrong about that, then the genie's already out of the bottle.'

He paused and gazed at the wine still in the glass. *Which means Hector and Lucas were right to be cautious, right to be concerned about something from the past upsetting the present. They couldn't have known how potentially damaging it was all going to turn out to be, but their instincts were right. And if their instincts were right, then maybe their methods were as well. Maybe the means do sometimes justify the ends.' He emptied the glass and waited for Jumai to pour him another measure from the bottle, which was a satisfying Patagonian red a shipped up from the inner system in 2129, if the label was to believed.

The year of his birth, not that he attached any significance to that.