The Doctor tapped his chin reflectively.

Curton appeared with a young grey-suited technician in tow.

'There's a problem,' he said bluntly. 'The automatic launch sequence programme has been wiped, probably Monitor's doing. Somebody will have to stay behind to run the sequence manually.'

The import of his words sunk in. Susan said: 'It's not fair.

Just when we thought we'd got everything worked out.'

Ian sighed and said to Curton: 'Well, we've just got a key to our TARDIS back, so I suppose the Doctor can work the launcher. And we'll take the extra pa.s.sengers with us. But there's no guarantee we'll ever reach Mirath to meet up with you again.

'No, Chesterton, we can't take the others with us,' the Doctor said. 'These people need to stay together to make the colony work. It will need as many as possible... especially proven survivors like the NC2s. Their presence may mean the difference between the colony's success or failure.'

'But how can we manage it?' Barbara asked. 'Even the TARDIS can't be in two places at the same time.'

The Doctor looked deeply thoughtful. 'There might be a way. Mr Curton, arrange for the ship to be reloaded, including sufficient additional supplies. They must have storerooms here somewhere. Meanwhile, I shall see if I can provide you with s.p.a.ce for a hundred and fifty extra pa.s.sengers.'

Half an hour later the Doctor emerged from the TARDIS holding something in his hands that caused Ian to flinch and turn his head aside.

'What is it?'

Externally it was a cube about a foot across, formed out of small intersecting angled panels dimpled like miniature versions of the walls inside the TARDIS. What made it painful to look at was the impression that the panels formed corridors that stretched away into the cube for many yards.

'It's a portion of folded s.p.a.ce,' the Doctor explained. 'It can be used to provide extra room inside a TARDIS, or else serve as an emergency evacuation module... a sort of lifeboat, if you will. There should he enough spare power from the Lander's reactor to expand it until it is large enough externally for the NC2s to enter, but of course their actual ma.s.s will not register as payload. The android will know how it should be maintained.'

He made his way carefully towards the Lander's gangway.

'I have never had cause to use it before,' he added. 'I only hope its unorthodox removal doesn't interfere with the TARDIS's dimensional stability.'

An hour later the great hangar doors had been slid hack.

Outside clouds laced with lightning boiled over the rim of the plateau valley. Every few seconds the horizon lit up as another fragment of the falling moon struck Sarath. The sky to the south was a steady dull red. Earth tremors were becoming more frequent and several falls of rock had scarred the valley sides.

Curton, Plax, Nyra and the Susan android were the last to board the Lander. The Doctor shook hands with them, hesitated as he approached the android, then kissed it quickly on the forehead.

'I apologise for the way I treated you at first,' he said. 'I think you are very brave.'

'I have a good example to follow,' it replied.

'Thank you for finding Barbara,' said Ian to Curton.

'Just doing my job,' said Curton. 'Never give up while there's still a chance. Otherwise we wouldn't be here now, would we?'

'Everybody says colonising a new world is hard work,'

Plax said ruefully to Barbara and Susan. 'Oddly, my father is rather looking forward to it.'

'You're going to get more blisters,' Barbara told him.

'I thought of that,' Plax said brightly. 'I've taken an extra pair of gloves.'

'Now you must try to remember Lant as he would wish,'

the Doctor told Nyra.

'I can't believe he was really... a machine.'

'There is nothing necessarily wrong with being a machine,' the Doctor said, glancing at the android Susan. 'It all depends on the spirit within.'

They stood back and waved as the hatch closed and the steps retracted, then took their places at the hangar launch-control panel. The Doctor and Susan began pressing b.u.t.tons and turning dials.

The Lander's sledge cradle lifted gently as power was fed to the coils in its base. It glided silently through the hangar doors along the metal channel, supported by magnetic levitation while the fence coils mounted on either side drove it forward. Once clear of the hangar it began to pick up speed and accelerated rapidly away.

Halfway along the valley floor the indicators on the control panels showed the Lander reaching the speed of sound.

They saw dust blasted from the embankments as the pressure wave tore into them. A few seconds later a sonic boom rolled back along the trackway to the hangar.

The Lander was a silvery dot as it began the long curving climb up the far wall of the plateau. Suddenly a brilliant spear of white light sprang from its tail as its engines fired for the first time, adding their thrust to that of the sledge. High among the peaks, it leaped skywards off the end of the track.

Explosive bolts blew the cradle fastenings and the sledge a.s.sembly tumbled away. The Lander was on its own, a white star rising improbably upwards into the heavens.

Shielding their eyes against the wind whipping through the doors they watched the Lander pa.s.s into the boiling clouds.

For a few seconds they were illuminated from within by the flare of the Lander's engines, then the glow slowly faded from sight.

'I hope they make it,' said Ian.

'I'm sure they will, Chesterton,' the Doctor said.

'Do you think we might visit Mirath one day and see how they got on?'

'Perhaps, perhaps,' the Doctor said. 'Who knows what the future may bring?'

A blaze of yellow fire flashed across the southern sky. The ground trembled as compression waves rippled through the clouds. A thunderous roar beat down out of the heavens upon them.

'I think it's time we left!' Barbara shouted.

They ran for the TARDIS and gratefully closed its doors on the savage destruction outside. The Doctor crossed to the console and began throwing switches.

On the scanner they saw pieces of the cavern ceiling falling to earth. Searing light shone in through the open hangar doors and the TARDIS rocked as though a huge wave was washing over it.

Then the pulse of dematerialisation sounded and the shaking melted away as the dying world vanished in the mists of time and s.p.a.ce. Once again they were enveloped in the silent grey infinity of the interdimensional void.

Barbara sighed. 'Do you think you can take us somewhere peaceful for a change, Doctor?'

'And what had you in mind, Miss Wright?'

'Oh, a nice quiet country garden, perhaps?'

The Doctor smiled, his eyes twinkling, looking suddenly absurdly boyish. 'As always, I shall try my best,' he said.

Epilogue.

Every Founding Day on Mirath the people go to New Arkhaven City to pay their respects at the memorial.

Carved into its outer walls are the names of the first pioneers, together with a bas-relief of a s.p.a.cecraft resting on widespread landing legs. In a small chamber inside the memorial, protected by a gla.s.s-sided cabinet, sits a slender human-like figure formed out of metal and plastic. It is known simply as 'The Pilot'. Though it is hard to read any expression on its silvery face, many people believe it radiates an aura of calm serenity.

Inscribed on either side of the cabinet are two phrases familiar to everybody on the planet. One reads simply: NEVER FORGET The other is slightly ambiguous, since it is also said to refer in some way to the Pilot. It reads: ONE DAY WE SHALL RETURN.