Tegan was backing away, her face filled with terror.

Nyssa tugged at the Doctor's sleeve. 'Look, Doctor. Look at Tegan.'

The Doctor looked. 'This must be the cave from her dream.' He leaned forward. 'It's all right, Tegan, there's nothing to be frightened of.' He took her arm and tried to lead her up the steps.

Tegan pulled away.

'It's all right, Tegan,' said the Doctor again. 'There's nothing to be afraid of.'

Tegan backed away.

Nyssa said, 'Doctor, she can't hear you-remember?'

'Nevertheless, my dear Ambril,' Lon was saying, 'Your predecessor apparently believed in the Legend.'

'Yes, so he did!' said Tanha. 'Now what was the man's name?'

'His name was Dojjen, my lady,' said Ambril stiffly.

'Dojjen! Of course, that was it!' Tanha was delighted. 'Dojjen!'

'I am afraid Dojjen came to believe in so many things,' said Ambril sadly. 'He became very erratic towards the end.

Here in the cave system the real work was sadly neglected.'

'The real work?' asked Lon idly. 'Oh, I see. You mean poking about in the ruins. Digging for trinkets?'

'I mean archaeology, my Lord,' protested Ambril. 'I have tried to re-establish our work here on a scientific basis.'

'And I'm sure we are all very grateful,' said Tanha soothingly.

Ambril beamed. 'Shall we proceed into the Chamber of the Mara?'

Tegan was sitting on the top step of the flight that led up to the cave mouth, her back to the entrance of the cave. She was hunched forwards, her arms about her knees. It had taken all the Doctor's urgings to get her this far, and she would go no further.

'What are we going to do?' asked Nyssa. 'She can't go in. She's too frightened.'

'Well, you'll just have to stay with her. I'll go into the cave alone.'

The Doctor went up to the cave mouth, turned and gave them a rea.s.suring wave and then went inside.

The most famous exhibit in the caves was the carving known as the Great Snake. It occupied almost the whole of one wall of the Chamber of the Mara. Immense, malevolent, terrifying, the huge serpent seemed about to spring out of the solid rock into which it was carved. Between the open jaws was an empty socket.

Ambril peered up at it. 'Exquisite is it not?'

Lon nodded towards the empty socket. 'What was in its mouth?'

'The Great Crystal, my Lord. Purely decorative.'

'Where is it now? Is it lost?'

'Oh no, my Lord. It was removed from its socket when the Mara was destroyed. Traditionally, the safe keeping of the Great Crystal is the responsibility of the Director of Historical Research.'

'You, in other words?'

'At present I have that honour, my Lord,' And if anxious to change the subject, Ambril went on with his lecture. 'As you see, the image of the Mara is sculpted out of solid rock . . .'

Moving along the tunnel, the Doctor heard what sounded like the voice of some kind of tour guide. 'This imagery of the rearing snake is consistent throughout the mid-Sumaran period, with only insignificant variations . . .'

'Someone's very well-informed,' thought the Doctor. He headed towards the voice.

In the Chamber of the Mara, Ambril was still droning on. 'In the Sumaran Three period the head has a tendency to be marginally less p.r.o.nounced, but in general. . .'

By now even Tanha was losing patience. 'Oh, do be quiet, Director,' she pleaded. 'Just for a moment!'

Ambril fell silent.

For a long moment they all stared up at the great carved snake. So realistic were the stone coils that they seemed to writhe and twist, as if trying to break free.

The Doctor came quietly into the chamber and stood watching the little group.

Tanha shuddered. 'It really is horrible. I'm so glad the Legend of the Return is just a story.' She turned appealingly to Ambril. 'It is just a story, isn't it? You're quite sure?'

The Doctor stepped into view. 'No, I'm afraid it's not!'

Lady Tanha jumped, and gave a little scream. A huge helmeted figure stepped out of the shadows by the door and clamped a ma.s.sive forearm across the Doctor's throat.

The Federation bodyguards were never far away.

Tegan still sat hunched up at the top of the steps outside the cave, watched anxiously by Nyssa.

A pa.s.sing hawker decided that they were a couple of likely prospects and came ambling over with his tray.

Not surprisingly he was selling snakes, garishly-painted articulated toys that wriggled convincingly with the aid of a stick. 'Look here, ladies,' he called. 'Souvenir snakes, very nice, very good!'

Nyssa looked at the tray and waved him away. 'No thank you, not now.'

The hawker turned his attention to Tegan. Picking up a snake from the tray, he leaned over and wriggled the snake in her face. 'Souvenir snake, lady?'

Tegan couldn't hear his words of course, only the silent rushing sound of the Doctor's device. She looked up and saw the grimacing snake, the mouthing face of the hawker and behind him the snake-mouth entrance of the cave. Suddenly Tegan leaped to her feet. She thrust the hawker aside and ran down the steps, disappearing down the narrow street that led to the market quarter.

'Tegan, come back!' called Nyssa. Then, realising that shouting was useless, she ran down the steps after Tegan.

The hawker shrugged his shoulders and wandered off.

The Doctor wriggled frantically, trying to keep his feet on the ground.

'There's really no need for this,' he gasped.

'This is a private view,' said Ambril indignantly. 'You have no business to be here.' He waved the bodyguard. 'Throw him out!'

The bodyguard looked to Lady Tanha for confirmation. She nodded, and he began heaving the struggling Doctor away. Lon, however, welcomed any interruption to Ambril's lecture. 'Wait!' he ordered. 'At least let the man have his say.'

'But why, my Lord,' spluttered Ambril. 'After all, the man is quite clearly deranged.'

'Is he?'

'Of course he is!'

'Lon, please,' said Tanha wearily. 'I really think the Director should deal with this.'

Still in the grip of the giant bodyguard, the Doctor shouted, 'Director?

Director of what?'

Ambril drew himself up. 'I am Director of Research effort into the Sumaran era.'

'Are you indeed? Then you may be able to help.'

'I think not,' said Ambril haughtily. 'Throw the fellow out.'

'Just a moment, Ambril,' snapped Lon. 'First let him speak.' He smiled mockingly at his mother. 'After all, it has been suggested that I take more interest in our legends!'

The bodyguard released the Doctor who straightened his collar indignantly. 'I should think so too! No then, I have something very important to tell you -about the Mara.'

Nyssa reached the far end of the street just in time to see Tegan disappearing into the market quarter. She tried to follow her, but Tegan was out of sight, lost in the teeming crowd. Giving up the hopeless search, Nyssa turned and headed back towards the Cave of the Snake.

Tegan meanwhile was still lost in her strange, silent world. Jostled by the crowds she stumbled along, staring wildly at the silently mouthing faces all around Suddenly it all became too much for her. The colourful crowded scene began spinning around like a kaleidoscope, and Tegan fainted, collapsing in a heap before a fortune-teller's booth - right at the feet of Madame Zara, the fortune-teller.

The Doctor's story of renewed danger from the Mara was meeting a sceptical response. Tanha looked baffled and Ambril was openly scornful.

Lon was the most sceptical of all. 'And where, according to you, is the Mara now?'

The Doctor said carefully, 'At present it exists as a latent force in the mind of my companion.'

'Does it really?'

'The Mara is using her dream to increase its power, Eventually it will take over her mind altogether-if it can. But I've put together a device to inhibit this, at least temporarily.'

'How very resourceful! And where is this young lady?' The mockery in Lon's tone was obvious now.

'She's outside. Why don't you come and meet her?'

Lon shrugged. 'Why not? Take us to her.'

'Certainly. If you'll follow me?'

The Doctor led them back along the access tunnel and outside the cave - where he saw Nyssa hurrying up the steps to meet him.

'Nyssa! Where's Tegan.'

'Is this your companion?' asked Lon.

The Doctor ignored him. 'What's happened, Nyssa?'

Nyssa was gasping for breath. 'She's gone. Doctor.'

Lon turned to Ambril and Tanha and said mockingly, 'Oh dear! She's gone, apparently. How sad!'

Nyssa told the Doctor what had happened. 'It all happened so quickly.

She just took fright and ran."'

'You have disappointed me, Doctor,' said Lon. 'I really should have you punished.'

The Doctor said urgently, 'Come on, Nyssa, we must find her.'

The bodyguard took a step forward, his hand on his sword.

'Oh let them go,' said Lon wearily. 'After all, what's the point?'

The Doctor and Nyssa had no more luck in finding Tegan than Nyssa had on her own. The press of the crowd made it difficult to move at any speed, and it was impossible to pick out one person amongst so many.

'Oh, this is hopeless,' said the Doctor at last. 'She was frightened you say?'

'Terrified.'

'Well, let's go back to the TARDIS. She might try to find her way back there.'

But there was no sign of Tegan in the TARDIS either.

Nyssa looked despairingly at the Doctor. 'Where can she be?'

'Who knows? As long as she's wearing the anti-dreaming device she should still be safe.'

'And if she takes it off?'

'I don't know,' said the Doctor helplessly. 'I just don't know.' He began pacing about the control room. 'There's so much we don't know. Why has the Mara returned? Why now, after so long? What does it want?'

Tegan awoke to find herself slumped in a chair inside a cramped and gloomy booth. Faded red and green hangings draped the walls, and a sinister hooded figure was hovering over her. Tegan gasped and shrank back and the sinister figure pushed back its hood to reveal a plump, rather motherly face looking at her in concern.

Madame Zara patted Tegan's shoulder. 'There! Feeling better dear?'

Tegan stared blankly at her.

Madame Zara reached forward and slipped the earpieces from Tegan's ears. 'There, that's better. Can you hear me now?'

'No,' protested Tegan feebly. 'I mustn't take it off.'