And it also explains another mystery. I asked Dave directly: why was I allowed to land on Europa, when everyone else has been turned away for centuries? I fully expected to be!

The answer's ridiculously simple. The Monolith uses Dave – Halman – from time to time, to keep an eye on us.

Dave knew all about my rescue – even saw some of the media interviews I made, on Earth and on Ganymede. I must say I'm still a little hurt he made no attempt to contact me! But at least he put out the Welcome mat when I did arrive...

Dim – I still have forty-eight hours before Falcon leaves – with or without me! I don't think I'll need them, now I've made contact with Halman; we can keep in touch just as easily from Anubis... if he wants to do so.

And I'm anxious to get back to the Grannymede as quickly as possible. Falcon's a fine little spacecraft, but her plumbing could be improved – it's beginning to smell in here, and I'm itching for a shower.

Look forward to seeing you – and especially Ted Khan.

We have much to talk about, before I return to Earth.

TRANSMIT

STORE

On the whole, it had been an interesting but uneventful decades, punctuated by the joys and sorrows which Time and Fate bring to all mankind. The greatest of those had been wholly unexpected; in fact, before he left for Ganymede, Poole would have dismissed the very idea as preposterous.

There is much truth in the saying that absence makes the heart grow fonder. When he and Indra Wallace met again, they discovered that, despite their bantering and occasional disagreements, they were closer than they had imagined. One thing led to another including, to their mutual joy, Dawn Wallace and Martin Poole.

It was rather late in life to start a family – quite apart from that little matter of a thousand years – and Professor Anderson had warned them that it might be impossible. Or even worse...

'You were lucky in more ways than you realize,' he told Poole. 'Radiation damage was surprisingly low, and we were able to make all essential repairs from your intact DNA. But until we do some more tests, I can't promise genetic integrity. So enjoy yourselves – but don't start a family until I give the OK.'

The tests had been time-consuming, and as Anderson had feared, further repairs were necessary. There was one major set-back – something that could never have lived, even if it had been allowed to go beyond the first few weeks after conception – but Martin and Dawn were perfect, with just the right number of heads, arms and legs. They were also handsome and intelligent, and barely managed to escape being spoiled by their doting parents – who continued to be the best of friends when, after fifteen years, each opted for independence again. Because of their Social Achievement Rating, they would have been permitted – indeed, encouraged – to have another child, but they decided not to put any more of a burden on their astonishingly good luck.

One tragedy had shadowed Poole's personal life during this period – and indeed had shocked the whole Solar community. Captain Chandler and his entire crew had been lost when the nucleus of a comet they were reconnoitring exploded suddenly, destroying Goliath so completely that only a few fragments were ever located. Such explosions – caused by reactions among unstable molecules which existed at very low temperatures – were a well-known danger to comet-collectors, and Chandler had encountered several during his career. No one would ever know the exact circumstances which caused so experienced a spaceman to be taken by surprise.

Poole missed Chandler very badly: he had played a unique role in his life, and there was no one to replace him – no one, except Dave Bowman, with whom he had shared so momentous an adventure. He and Chandler had often made plans to go into space together again, perhaps all the way out to the Oort Cloud with its unknown mysteries and its remote but inexhaustible wealth of ice. Yet some conflict of schedules had always upset their plans, so this was a wished-for future that would never exist.

Another long-desired goal Poole had managed to achieve – despite doctor's orders. He had been down to Earth: and once was quite enough.

The vehicle in which he had travelled looked almost identical to the wheelchairs used by the luckier paraplegics of his own time. It was motorized, and had balloon tyres which allowed it to roll over reasonably smooth surfaces. However, it could also fly – at an altitude of about twenty centimetres – on an aircushion produced by a set of small but very powerful fans. Poole was surprised that so primitive a technology was still in use, but inertia-control devices were too bulky for such small-scale applications.

Seated comfortably in his hoverchair, he was scarcely conscious of his increasing weight as he descended into the heart of Africa; though he did notice some difficulty in breathing, he had experienced far worse during his astronaut training. What he was not prepared for was the blast of furnace-heat that smote him as he rolled out of the gigantic, sky-piercing cylinder that formed the base of the Tower. Yet it was still morning: what would it be like at noon?

He had barely accustomed himself to the heat when his sense of smell was assailed. A myriad odours – none unpleasant, but all unfamiliar – clamoured for his attention. He closed his eyes for a few minutes, in an attempt to avoid overloading his input circuits.

Before he had decided to open them again, he felt some large, moist object palpating the back of his neck.

'Say hello to Elizabeth,' said his guide, a burly young man dressed in traditional Great White Hunter garb, much too smart to have seen any real use: 'she's our official greeter.'

Poole twisted round in his chair, and found himself looking into the soulful eyes of a baby elephant.

'Hello, Elizabeth,' he answered, rather feebly. Elizabeth lifted her trunk in salute, and emitted a sound not usually heard in polite society, though Poole felt sure it was well-intentioned.

Altogether, he spent less than an hour on Planet Earth, skirting the edge of a jungle whose stunted trees compared unfavourably with Skyland's, and encountering much of the local fauna. His guides apologized for the friendliness of the lions, who had been spoilt by tourists – but the malevolent expressions of the crocodiles more than compensated; here was Nature raw and unchanged.

Before he returned to the Tower, Poole risked taking a few steps away from his hoverchair. He realized that this would be the equivalent of carrying his own weight on his back, but that did not seem an impossible feat, and he would never forgive himself unless he attempted it.

It was not a good idea; perhaps he should have tried it in a cooler climate. After no more than a dozen steps, he was glad to sink back into the luxurious clutches of the chair.

'That's enough,' he said wearily. 'Let's go back to the Tower.'

As he rolled into the elevator lobby, he noticed a sign which he had somehow overlooked during the excitement of his arrival. It read:

WELCOME TO AFRICA! 'In wildness is the preservation of the world.' HENRY DAVID THOREAU (1817-1862)

Observing Poole's interest, the guide asked 'Did you know him?'

It was the sort of question Poole heard all too often, and at the moment he did not feel equipped to deal with it.

'I don't think so,' he answered wearily, as the great doors closed behind them, shutting out the sights, scents and sounds of Mankind's earliest home.