A penitent Ibbotson stood, head bowed low, in the Headmaster's study. His delight at driving in the Brigadier's car, which had so swiftly turned to terror at Turlough's recklessness, then to relief at his miraculous escape, had become sheer funk in front of Mr Sellick.

'You realise, Ibbotson, that what you did was a criminal offence.' Chastising Ibbotson, the Headmaster felt none of the unease he had experienced with Turlough. 'If it wasn't for the good name of the school, I'd hand you both over to the police. I shall be writing to your parents, needless to say.'

Ibbotson stumbled out into the corridor, tears of mortification p.r.i.c.king at his eyes - straight into the arms of the Brigadier.

'Ah, Ibbotson! And what have you got to say for yourself?'

'Please, sir, I'm sorry, sir. It wasn't my fault. Honestly.

I'm very sorry, sir...' He fled down the corridor like a terrified rabbit.

The Brigadier, who was a kind man at heart, wished that he had been a little less brusque, but he concealed his sympathy from the Headmaster, who emerged at that moment from his study. 'I trust you flogged that young man within an inch of his life,' he bl.u.s.tered.

'Thank you, Brigadier. I think we should wait until Turlough has recovered before we take any disciplinary action.'

The Brigadier grunted.

'I'm sure you'll agree, we must do what's best for the school.'

'If you say so, Headmaster,' said the Brigadier, thinking of his no-claims bonus. 'Mind you,' he continued, as they walked down the corridor together, 'we can't really take it out on Ibbotson. He was led into this by Turlough. Got a rotten one there.'

The Headmaster was silent for a moment, remembering those cold, penetrating eyes. 'I'm not so sure. I've had a word with Turlough. His story is that he went along to protect Ibbotson.'

'Cunning as a fox. You don't believe him, of course.'

'I don't know. But I'd be reluctant to jeopardise the boy's future.'

'Have you spoken to his parents?'

'I thought you knew. They're dead. I deal with a solicitor in London. A very strange man he is too.'

Ibbotson looked round to make sure that the coast was clear, then quietly opened the sick-bay door.

Turlough heard his friend come in, but continued to stare vacantly at the ceiling.

'Are you awake, Turlough?'

'What do you want?'

Ibbotson had no clearly defined reason for the visit, but in his wretchedness needed to talk to somebody somebody.

'The Head's going to write to my parents. The police may be called in to investigate. We could be expelled,' he blurted out.

Turlough smiled. 'It's all right, Hippo. I explained to Mr Sellick. I told him it was all my fault.'

'I say, did you really!'

Turlough grinned maliciously. 'So you won't get the boot. Just beaten I expect.' He laughed at the look of dismay on Ibbotson's face.

'They'll beat you you when you're better.' when you're better.'

'Oh no they won't!' Turlough threw back the bedclothes, swung his legs to the floor, and stood up fully dressed.

'You can't get up till Doctor Runciman says so!'

Turlough opened the door. 'Goodbye, Hippo.'

Ibbotson's heart sank. His only friend was abandoning him. 'Turlough, you can't leave me on my own!' he pleaded.

Turlough lingered in the doorway.

'Please, Turlough!'

An idea occured to the older boy. The company of Ibbotson might prove rea.s.suring - or at least a source of amus.e.m.e.nt.

Turlough looked at Ibbotson. He didn't speak. But his eyes said, 'Follow me if you dare!'

Ibbotson followed Turlough down the pa.s.sage behind the Seniors' Dormitory, past Matron's sitting-room, and onto the landing at the top of the fire escape. Turlough moved as anxiously as the more timorous Ibbotson; to be discovered now would be disastrous.

The coast was clear. With a terrible clatter they ran down the metal stairs. They reached the bottom and hugged the wall, panting nervously. So far so good.

A quick dash across the gravel, over the lawn, and a line of tall privet hid them from the school. Turlough stopped running. Ibbotson caught up and walked beside him, too out of breath to speak. Together they skirted the willows at the end of the lake.

They came to the hill. A steep path led upward between the trees to where, on the summit, they could see the obelisk.

For a moment Turlough stood and gazed at the distant monument, then without a word began to climb the path.

'Turlough!' called Ibbotson. 'Where are we going?'

Turlough didn't even glance over his shoulder.

Desperate not to be left behind, Ibbotson scrambled after his friend, who seemed to have forgotten the other boy as he dashed up the hill.

'Turlough, wait!' Ibbotson had a st.i.tch in his side and his legs ached. He stood gasping for breath, the sweat pouring down his face.

Turlough had a lead of some hundred yards as he disappeared into the trees that ringed the crown of the hill.

'Turlough!' Ibbotson forced himself to go on.

He reached the wood and looked round for his friend, calling out as he walked between the trees.

The first thing Ibbotson noticed was the light. There was no way the sun could penetrate the canopy of leaves, yet the base of the oak tree ahead was brilliantly illuminated. Ibbotson stood still, frightened by the strange aurora. Then he saw Turlough.

The other boy was standing beside the trunk of the tree, his hands cupped and raised above his head, as if in some pagan rite. Ibbotson felt like an intruder, but his curiosity urged him forward. As he drew closer he realised that his friend's outstretched arms were at the centre of the unnatural radiance. He became aware that Turlough's lips were moving, as if in conversation with an unseen person.

'Turlough, what's happening! Who are you talking to?'

he called - and instantly regretted his impetuosity.

The light went out. Turlough, who had been oblivious of his friend's approach, wheeled round, startled and guilty. As he turned, Ibbotson thought he glimpsed a small, square fragment of gla.s.s that Turlough slipped quickly into his pocket, before dashing off in the direction of the obelisk.

'Turlough! Wait for me!' Ibbotson stumbled through the thick compost of leaves and out into the small clearing on the summit. He blinked owlishly in the sunlight.

Turlough stood lazily beside the base of the obelisk. As Ibbotson walked towards him, the older boy smiled casually as if the two of them had just met at a bus stop.

'Now what?' said Ibbotson 'We wait,' said Turlough.

Both Tegan and Nyssa disliked the cloying sumptuousness of the alien ship. The Doctor, though he had said nothing to the girls, was equally disturbed by the stifling splendour.

Yet he continued to explore.

A narrow gangway led from a short flight of stairs into a wide gallery. Though the ornate style of the rest of the ship was still much in evidence, this area had a more functional aspect than elsewhere.

'The control centre,' observed Nyssa, as she joined the Doctor who was already examining a large panel in the centre of the room.

'Could you fly this thing?' asked Tegan.

But the Doctor was far too interested in the controls.

'You don't fly a ship like this.' Nyssa turned from a bank of computer screens. 'It's in perpetual orbit.'

'Amazing,' muttered the Doctor. He pointed to an indicator on the desk. 'This ship has been in orbit nearly three thousand years.'

'No wonder there's no one on board.' Tegan grinned, though she felt repulsed at the idea of being part of a flying mausoleum.

'Doctor, come and look at this!' Nyssa had wandered over to a recess in the far corner of the room. Tegan followed the Doctor across, but she couldn't understand the interest of the other two. After all, the alcove they were examining with such enthusiasm was entirely empty.

'A transmat terminal' explained the Doctor, examining the computer keyboard on the wall.

'And in the transmit mode,' added Nyssa.

'Perhaps the crew escaped in the life-raft,' Tegan joined in nervously. She didn't like the idea of particle transmission one little bit. Like travelling in a food-mixer.

She had visions of coming out as taramosalata. Not that they'd ever get her in one of those things.

But, like a 36 bus, the thing was curiously non available.

'Someone left the ship in the capsule about six years ago.' The Doctor had begun to make sense of the complex navigational data.

'Where to?'

The Doctor smiled and turned back to the keyboard. He swiftly converted Tegan's question into language the computer could understand.

Back came the answer.

'Earth!' The Doctor read the information from the display. 'The ship's...o...b..t takes it in range for seven years.'

'If the seven years are up, someone might come back.'

Tegan looked anxiously at a red light that had started to flash in the terminal bay.

'Any time,' agreed the Doctor. 'I think we ought to get back to the TARDIS.' There was no mistaking the sudden urgency in his voice.

Turlough and Ibbotson stood silently beside the obelisk.

Turlough was nervous, afraid of yet another disappointment. Perhaps it had all been an illusion. His fingers tightened round the nugget of crystal in his jacket pocket; that was real enough.

He looked around him. There was a splendid view over the tops of the trees into the valley below; the sun dappling the lake; the old house seeming to doze in the afternoon warmth; the distant pirouette of white-flannelled boys on the cricket pitch. How typical of the Earth - of England!

So complacently pastoral! Hardly the time and place for acts of destiny.

Little did Turlough know about the terrible plan of which he was the merest part; a final solution, after which the light would be turned into darkness, evil become good and good be evil.

Nor did he realise that at that very moment, out in s.p.a.ce but within transmat range of the obelisk, the Doctor, to satisfy his companions' curiosity, had activated the search-and-reveal programme in the control centre of the red ship.

As the location of the transmat capsule was beamed back from Earth to the ship, so the camouflage circuit cut out.

Ibbotson gasped as a gleaming silver sphere materialised between the trees.

Turlough smiled.

Ibbotson stared in amazement. 'What is it?' he stammered.

'Don't you recognise a transmat capsule when you see one?' Turlough walked confidently to the shining globe. A segment slid back to reveal a door.

Ibbotson stood petrified. 'Keep back!' he yelled.

Turlough continued towards the dark cleft in the side of the sphere.

'Turlough!'

As Turlough stepped through the opening, the panel slid back, enclosing the boy. Ibbotson watched, sick with horror.

Then the sphere vanished.

Ibbotson blinked. He rushed forward to the s.p.a.ce between the trees, but there was no sign of the sphere - or of Turlough.

He began to tremble. A wave of blind panic surged over him and he dashed off down the hill as fast as his legs would carry him.

Brigadier Lethbridge-Stewart had been to look at his car in the local garage. It had been like visiting a loved one in an ill-equipped cottage hopsital. He suspected the old girl was not getting the treatment she needed, and there had been sharp words with the mechanic, followed by a long and acrimonious conversation with his insurance company.