Tegan's eyes were screwed tightly shut. 'Something ... in here. Over there. Mustn't look. Mustn't ever look. I'm safe if I don't look.'

'Tegan!'

'No . . . no . . .' gasped Tegan.

The Doctor's voice was firm. 'Tegan, you are perfectly safe. You must look. We need to know what is in there.'

Tegan's eyes opened wide. Slowly her head turned to her left and her face twisted with fear as she focused on some unseen horror. Suddenly the fear faded from her face, and it became cold and hard. She glared angrily at the Doctor and the voice that came from her lips was deep and harsh and terrible.

'Go away?

The Doctor knew that the voice was not Tegan's voice. It was the voice of the Mara.

The old market quarter sprawled through the warren of streets that surrounded the palace. They were narrow, winding streets, roughly cobbled, and they were lined with shops and stalls and booths of every kind. Many of the stalls sold food and drink and the warm air was heavy with the smells of cooking fires, roast meats, baking pastries and spicy sweetmeats.

Ma.n.u.ssans from all over the planet thronged the narrow alleys: lean brown hillmen, robed and hooded; richly dressed merchants and officials; brawny labourers; off-duty soldiers in steel and leather. They jostled through the ever-busy streets, eating and drinking, turning over the goods, buying and selling and haggling, laughing and chattering and arguing and crying their wares. Loudest of all were the showmen, bellowing the delights of the various attractions inside their booths.

One of the noisiest was Dugdale, a st.u.r.dy barrel-chested man with a voice like a bull. Resplendent in a military-looking tunic with tarnished gold froggings, a gold sash and a somewhat moth-eaten fur hat, Dugdale stood before his Hall of Mystery. On the front of the long booth there was painted a huge coiled snake, drawn in such a way that the entrance to the hall led through the mouth of the snake.

'Roll up,' roared Dugdale. 'How about you, sir? You Madam? Step this way if you would be so kind. I invite you to take the most exciting journey of all, the voyage inside. The journey to meet yourself The crowd ignored him. Undeterred, Dugdale ploughed on. 'I address you in the silence of your own hearts. I offer my personal challenge. Dare you bear witness to what the Mara shows? Dare you gaze upon the Unspeakable? Dare you come face to face with the finally Unfaceable?'

He paused and added hopefully, 'Children half price!'

The crowd flowed unheedingly.

Dugdale sighed. Trade had been slack for weeks now, and for no good reason. Maybe it was the excitement of the approaching ceremony.

Though you'd think that would increase the appeal of an attraction that dared to use the Mara itself as a come-on. He thought about going over to the tavern for a mug of wine to cool his throat.

Suddenly Dugdale spotted a swirl of movement just ahead. A tightly-knit little group was forcing its way along the street, burly guards clearing the way before them. n.o.bs, thought Dugdale in satisfaction. A party of aristocrats from the palace, out for a little slumming. The kind of people who carried purses full of gold coins. Hopefully, he raised his voice. 'Step this way, please. Come face to face with the truth about yourselves. Come along now, please.' The little group came level with his booth, and showed every sign of moving straight past it.

In desperation Dugdale stepped out in front of them, addressing a richly-clad young man who strode a little ahead of the rest. 'You sir, for instance. You!'

The young man stopped, and looked coldly down at him. 'Are you addressing me?'

Undeterred, Dugdale pressed on with his spiel. 'Now, sir, you have the look of a humble seeker after life's truth.'

'Do I really?' There was a silky menace in the young man's voice.

'Of course you do! Now sir, if you'd care to step inside . . .'

'Do you know who I am?'

A little crowd was gathering. Instinctively Dugdale played up to it. 'No, young man, I do not! Nor do these good people. Do tell us. Who are you?'

By now the crowd should have been joining in the mockery. But no one was laughing. The rest of the group had come up by now. Dugdale saw the richly dressed woman, and the high official hovering deferentially at her elbow, the brawny Federation bodyguards in their terrifying mask-like helmets.

Suddenly Dugdale's head felt loose upon his shoulders. He bowed low.

'I beg your pardon, my Lords, my Lady. 'I'm sure I didn't mean to give offence.'

To Dugdale's relief the woman smiled graciously, dismissing the incident. She moved on her way, escorted by the official and by her bodyguards. But the young man stayed where he was, sneering down at Dugdale. 'Well, what's in there?'

'In there?' babbled Dugdale.

'Yes. What exactly does one face in your shoddy little booth?'

'Mirrors, my Lord,' said Dugdale miserably.

'Mirrors?'

'Yes, my Lord. Distorting mirrors. That's all. People are amused.'

'Are they really?'

'Yes, my Lord. Generally.'

The woman had paused a little way ahead. 'Lon,' she called, 'Are you coming?'

'Coming, Mother.'

With a last chilling glance at Dugdale, the young man stalked away.

'Lon' thought Dugdale. He had been exercising his wit at the expense of the son of the Federator!

Dugdale leaned back against the facade of the Hall of Mirrors sweating with relief. He'd missed his purse of gold, but at least his head was still where it belonged.

The Doctor was making some adjustments to his hypnotic device. Tegan lay back on the bed, apparently quite calm and relaxed.

Nyssa said worriedly, 'That voice, Doctor, what was it?'

'The Mara - speaking through Tegan's mouth.'

Nyssa tried to remember the Doctor's account of events on Deva Loka.

'I thought you said there was a physical change when people were possessed by the Mara?'

'There is. It happens as the victim's mental resistance weakens. But this time I can prevent it.'

'How?'

The Doctor tapped the device round Tegan's neck. 'With this. It can be adjusted to inhibit the production of the brain waves a.s.sociated with dreaming. It can't be used indefinitely, but it will give us a little time.'

'To do what?'

'We must find the cave - the cave of the snake mouth from Tegan's dream.'

'It's a real place then?'

'Oh yes,' said the Doctor definitely. 'What's more, I would guess that it's somewhere very close to us.'

The entrance of the Cave of the Snake was set into a low rocky hill on the outskirts of the oldest part of the city. The rock round the cave mouth had been carved into an elaborate snake's head, and, just as in Tegan's dream, the entrance of the cave formed the mouth of the snake. A flight of time-eroded stone steps led up to the gaping black hole.

'This,' said Ambril, 'is the entrance to the cave system itself.'

Tanha nodded, remembering. 'I had forgotten how impressive it is.'

Ambril looked pleased.

Lon, as usual, looked profoundly bored.

Emerging from the TARDIS, the Doctor, Nyssa and Tegan found themselves beside some empty booths in a quiet corner of the market-place. Tegan gazed calmly about her, looking rather as if she were sleepwalking.

The Doctor closed the TARDIS door behind them. 'Now, remember Nyssa, Tegan is experiencing total exclusion of all outside sound. You must be her ears.'

Nyssa nodded. 'But surely she can't dream now? She's awake.'

'Dreams are occurring in the mind all the time,' said the Doctor solemnly. 'Come on, we must hurry!'

By now, Ambril and his party had climbed the steps and were standing just inside the entrance to the cave.

They were in semi-darkness, though lights gleamed deeper in the caves.

Lon yelled into the darkness. 'h.e.l.lo!' His voice echoed around the cave.

'h.e.l.lo-o-o.'

Ambril winced. 'The cave system itself is a natural geological formation, worn out of the solid rock over hundreds of thousands of years by a now-vanished underground river.'

'h.e.l.lo!' yelled Lon again. Again there came the echo. 'h.e.l.lo-o-o.'

'Lon!' said Tanha reprovingly. She smiled apologetically at Ambril.

Ambril sighed and continued. 'The Chamber of the Mara is the largest natural cavern thus formed. Many of the most important archaeological finds -'

Lon was staring round the vast shadowy cave, 'Big isn't it?' he interrupted.

'Beg pardon, my Lord?'

'This place. It's big.'

'Yes, I suppose it is,' said Ambril patiently.

'h.e.l.lo!' yelled Lon once again.

'h.e.l.lo-o-o . . .' came the echoes.

Ambril sighed.

The Doctor, Nyssa and Tegan threaded their way through the bustling market. Nyssa and the Doctor looked round eagerly, taking in the noisy colourful scene. To Tegan in her silent world things were very different.

She felt trapped in a meaningless confusion, filled with eerily-mouthing faces that made no sound. She could see the Doctor talking animatedly to a man at a nearby stall, and she saw the man pointing down one of the narrow side streets. The Doctor came back towards them.

'What did he say, Doctor?' asked Nyssa.

'I was right, it seems. There's a cave system at the edge of town, and the entrance fits the description exactly. It's this way.'

The Doctor led them towards the caves, uncertain what they would find there. One thing was certain. Only by finding and confronting the Mara once again, could he free Tegan's mind from the evil within.

3

Voice of the Mara

Still in his role of guide, Ambril ushered his party down the steeply sloping tunnel that led into the caves.

The entire cave system had been converted into a kind of rambling underground museum, with particularly interesting areas discreetly illuminated.

Ambril paused before one such section, a huge area of cave wall divided into separate panels, each panel covered with faded figures and symbols. Little stick-man figures were scattered about the panels, and it was noticeable that dotted energy lines from their heads came together in a diagrammed crystal which filled most of the last-but-one panel. The last panel of all was blank, as if the remains of the picture had been deliberately sc.r.a.ped away.

Ambril looked lovingly at the mural. 'This wall, known as the Pictogram, const.i.tutes an invaluable record of the Sumaran era. Of course, academic interpretations of the precise meaning differ considerably.

However, paying scrupulous attention to detail, and not allowing our imagination to run away with us, we can form the glimmering of an idea as to what these pictograms may mean . . .'

Ambril droned on and Tanha listened with her unvarying politeness.

Lon said abruptly. 'What about the Legend?'

Interrupted in mid lecture, Ambril blinked at him.

'The Legend, my Lord?'

'The Legend of the Return. Do you have an opinion?'

'Yes, my Lord, I'm rather afraid I do.'

'Well?''

Ambril drew himself up. 'The Legend of the Return is nonsense. Pure, superst.i.tious nonsense invented by the people, simply to give themselves something with which to frighten their children. It has no basis, neither speculative nor proved, in historical fact!'

From the bottom of the long flight of steps, the Doctor stared up at the Cave of the Snake in admiration.

'Extraordinary, isn't it?'