Ian opened his eyes and then groggily struggled into a sitting position. 'Barbara...' he croaked weakly, cradling his aching head in his hands.

'Where is she?' cried the Doctor, directing the torchbeam around the partly demolished cave.

Ian painfully extricated his legs from underneath the stones and tried to remember. 'She... she was outside... on the cliff...' he mumbled, still dazed and shocked.

The Doctor helped him to his feet. 'As soon as you have got your breath back, we shall go and find her,' he said, dusting off Ian's jacket. 'The whole roof seems to have collapsed over there...'

Ian stared along the torchbeam at the impenetrable wall of fallen rock. 'It's completely blocked the tunnel, Doctor!'

he gasped, clasping the Doctor's sleeve. 'I'm afraid Barbara's been...' He winced with pain and tried to relax his wrenched spine.

'I hope there will not be any further falls,' the Doctor muttered grimly, turning to glance at the battered police box. 'I fear the TARDIS could not stand up to too much more of this sort of treatment.'

'I don't think I I could either,' Ian complained bitterly, trying to gather his shattered wits. 'Listen, Doctor, I don't think this was an accident.' could either,' Ian complained bitterly, trying to gather his shattered wits. 'Listen, Doctor, I don't think this was an accident.'

The Doctor shone the torch in Ian's face and peered at him anxiously, unsure of the young man's state of mind.

'Not an accident? What on Earth do you mean?'

Ian clung to the Doctor's arm for support and struggled to collect his thoughts. 'Well, there was this... outside the cave we met this... it came up behind us...' he mumbled helplessly.

' It It came up behind you? What came up behind you?' came up behind you? What came up behind you?'

demanded the Doctor impatiently.

'This thing... It was horrible... Hideous... With a face like one of those Aztec mask things... But it was alive... It spoke to us...'

The Doctor nodded mysteriously to himself. 'With red eyes and talons and sabre fangs...'

Ian nodded eagerly. Then he stared wide-eyed at the Doctor. 'Yes, but how did you know?'

The Doctor smiled. 'This is the planet Dido, Chesterton. I have been here before. In fact, I know it quite well. The inhabitants are extremely hospitable.'

Ian looked aghast. ' Hospitable! Hospitable! Well, this thing certainly wasn't at all hospitable! It ordered me to come and fetch you while it forced poor Barbara to stay outside...' he protested, his words falling over one another as his memory grew clearer. 'Then when I came into the cave there was this terrific bang and the tunnel collapsed behind me.. Well, this thing certainly wasn't at all hospitable! It ordered me to come and fetch you while it forced poor Barbara to stay outside...' he protested, his words falling over one another as his memory grew clearer. 'Then when I came into the cave there was this terrific bang and the tunnel collapsed behind me..

Thoughtfully the Doctor shone the torch slowly round the cave, while Ian, finding his strength gradually returning, staggered across to the huge mound of debris brought down by the explosion and started trying to shift the rocks blocking the tunnel. But after only a few seconds'

breathless struggle, he collapsed exhaused.

'It's no good, we shall have to find another way out of here,' the Doctor told him, still shining the torch around the walls. 'a.s.suming, of course, that there is one,' he added pessimistically. 'This figure who accosted you, Chesterton, was it armed?' The Doctor suddenly inquired.

Ian thought for a moment. But even thinking proved painful. 'I... I don't think so... Oh yes, Doctor...' Ian held up his hands. 'It was carrying a sort of club thing with crystals or something at the end... It was about this long.'

The Doctor compressed his lips and nodded. 'That could account for it,' he muttered with a preoccupied air.

'The last time I visited this planet the Didoi were just perfecting a portable sonic laser for use in engineering projects.'

Ian groaned and frowned at the rockfall. 'Some engineering!'

There was a brief silence.

'Now, how are you feeling?' asked the Doctor with sudden briskness.

'Not too bad, thanks.'

The Doctor stretched out a hand. 'Well, don't just lie there groaning! Let us get started!'

With the Doctor's help Ian hauled himself back onto his feet.

'At least there do not appear to be any broken bones,'

the Doctor declared, tugging his hand free and striding purposefully towards the TARDIS.

Ian dusted himself down. 'Thanks, Doctor, that's the most thorough medical check-up I've ever had in my life!'

he said, scowling resentfully.

The old man was busy investigating a deep narrow crevice almost hidden behind the police box. 'I have never claimed to be an expert in Hippocratic affairs,' he retorted, probing the niche with the penetrating torchbeam. 'Do come along, my boy. I think this may be our only chance of finding Barbara.'

Ian stumbled through the settling dust to join him. 'Did you say the inhabitants of this planet were hospitable?'

The Doctor manoeuvred himself into the fissure and shone the beam of the torch ahead along the dark defile.

'Extremely friendly. One of the most civilised species I have ever encountered. Now, do come along, Chesterton!'

His faraway voice echoed down the tunnel.

Ian squeezed himself through the crevice. 'Well, on first acquaintance with them I think I'll take the Daleks anyday,' he retorted, catching up and shoving brusquely past the Doctor where the twisting gully suddenly widened for a metre or two. 'Come along, Doctor, we've got to find Barbara quickly. I think your friendly inhabitants have forgotten their old-fashioned good manners!'

Gaping in astonishment at Ian's remarkable recovery, the Doctor followed, shining the torch ahead of them. 'Do be careful, my boy!' he warned.

'Don't worry, I will...' Ian said over his shoulder. 'These Didoi things are obviously jolly dangerous.' As they made their way cautiously along the musty, tortuous chasm which led deeper and deeper into the mountain the torch beam cast huge monstrous shadows on the walls around them. The Doctor stared thoughtfully at Ian's back. 'But I wonder why...' he said after a long silence. 'What can have happened to change their nature so profoundly?'

Before Ian could reply, a thunderous rasping bellow reverberated around them, almost as if the sides of the ravine were grating together in protest at their intrusion.

Ian stopped in his tracks and the Doctor careered into him and dropped the torch. It went out. The awesome sound had a shrill cutting edge that suggested the cry of some fantastic mechanical animal constructed by a mad subterranean Frankenstein.

They stood in the dusty darkness listening to the long dying echoes. Ian backed against the rock wall. 'Perhaps we're just about to find out, Doctor...' he whispered.

4.

Chalk white and motionless, Barbara lay spreadeagled at the bottom of the cliff', half-buried in a pile of rubble that had once been a simple but elegant dwelling. In one hand she still gripped the stem of a small thorn tree which she had managed to grab as she careered helplessly down the almost vertical scree. Her face and her hands were covered in scratches and bruises and dried blood, and one cheek was swollen like a huge purple fruit. Her clothes were torn and filthy and it would have been impossible for any observer to tell whether she was still breathing.

Then the sand and gla.s.sy stones nearby were scuffed aside as something approached and stood staring down at her, breathing heavily. Despite the pale curtain of haze across the reddish sun, a long shadow was cast across her inert body. It was like an image of Death itself.

The thorn tree was twisted out of her fist. Her arms were seized and she was dragged off the mound of debris and down onto the burning rock-strewn plateau. The shadow's breathing became faster and more laboured as it hauled her through the p.r.i.c.kly scrub, as if it was struggling to get its prey safely into its lair before any rival beast could rob it.

Keeping an anxious eye on the exterior hatchway, Vicki hurriedly finished arranging the blankets over her bunk, smoothing them as flat as possible to conceal something underneath with nervous little fluttering movements of her delicate hands.

She seemed to know that someone, or something, was coming towards the wreck and that it was not far away.

When she was satisfied that she had done her best, she sat down at the makeshift table fashioned out of an empty computer cabinet laid on its back and gazed through the hatch at the hot dry wilderness. Her head was c.o.c.ked on one side like a listening bird. Occasionally she glanced fearfully at the bunk, worried that her secret would be found out. Then, as a sudden afterthought, she jumped up and gathered up some of her rock specimens and brought them to the table. Settling down, she started sorting them into different orders as if she were cla.s.sifying her collection like an expert geologist.

A few minutes later she froze rigid. She had heard the dreaded lurching, scrabbling approach of the hybrid mutation that tyrannised her wretched castaway existence on the desolate arid world of Dido, the Thirteenth Planet.

Koquillion was coming.

The tall hissing figure loomed in the hatchway and manoeuvred itself into the compartment where it towered over her, hideous and threatening.

'You have been outside,' the creature rasped.

Vicki glanced over at the bunk and kept quiet. 'Stand up,' Koquillion commanded.

Vicki obeyed, backing away up the sloping curve of the hull.

'What were you doing out there?'

In sudden panic, Vicki tried to think. 'Walking,' she whispered.

The monster hissed angrily. 'In future you will venture no further than fifty of your metres from the wreck. Is that understood?'

Shaking with terror, Vicki nodded and mouthed 'yes'.

Koquillion turned and scanned the compartment with its bulbous red eyes. Then it stalked towards the bunk, its talons sc.r.a.ping against the hull with piercing shrieks that set Vicki's teeth on edge as she cowered by the radar. She held her breath as the creature reached for the blanket with its lobster claw. Her eyes stared in stark desperation. She gnawed her fist in abject terror.

Then Koquillion swung round. 'You were dragging something from the ruins,' it rasped.

Vicki racked her brain. She nodded. 'Yes... stones... I collect them...' She edged to the table and picked up one or two of her specimens. 'They are very beautiful.. She held them out, like an offering to appease an angry G.o.d. 'Your planet is very...'

Koquillion's claw slashed through the air and sent the stones smashing against the radar equipment. They shattered in a brilliant shower of multicoloured crystals.

Vicki drew back against the bulkhead, as far as she could away from the hissing horror.

Koquillion seemed to hesitate a moment, as if concerned that the delicate equipment might have been damaged. But the monster recovered its composure almost immediately. 'I am going to talk to Bennett. Remember, you both depend upon me for your very existence.'

As Koquillion turned towards the internal hatch leading through the debris to Bennett's compartment, Vicki mustered all her meagre courage and stepped forward. 'I... I heard a noise... up on the ridge...' Her voice trailed feebly into silence. She took a deep breath. 'It sounded like an explosion.'

Koquillion whipped round with a ferocious hiss. There was a terrible silence. Vicki hung her head submissively and waited, numb and almost senseless. Then she heard her tormentor speaking as if from a long way off: 'A s.p.a.cecraft arrived here.'

'The Seeker Seeker?' Vicki heard herself blurt out in a shrill and hysterical voice. She knew her question was absurd.

'The occupants were warlike,' Koquillion told her.

'They wanted to destroy. They could have destroyed you and pillaged your Astra Nine Astra Nine. I could not allow them to survive. I could not have protected them from my kind as I protect you and Bennett.'

'What did you do to them?'

'They have been entombed within the mountain. If they are not already dead they will soon perish of hunger and thirst and lack of vital oxygen...'

Koquillion's words struck a chill into Vicki's heart.

'You never gave them a chance,' she whispered. Then the anger erupted inside her. 'You could have...' she spat pa.s.sionately. Then her voice seized and she hung her head again. 'I am sorry,' she murmured. 'Please forgive me for my outburst.'

Koquillion glowered at her in silence for a moment.

'You should be grateful to me, you and Bennett!' he suddenly rasped, his voice like the sound of clashing blades. 'It is only my intervention that prevents my species from destroying you. Do not forget: I am your only only protection!' protection!'

Vicki knelt before the hideous spectre and clasped her hands together as if in prayer. 'Yes, I know, Koquillion...

And we are are grateful. Believe me, we are grateful.' grateful. Believe me, we are grateful.'

The monster's unblinking eyes gloated over her for a moment. Then it turned and manoeuvred itself through the internal hatch and hacked its way through the maze of cables and pipework to reach Bennett's compartment.

Vicki relaxed a little as she heard it rapping at the shutter. Then she heard Bennett's voice. 'No, you cannot come in...' it snapped in the staccato mechanical tone Bennett often used when she knocked with his food or water and then tried to open the shutter. How like a robot he sounded, she had often thought.

'It is Koquillion! Open the hatch!'

Vicki heard the customary click and then the grating slide back as the monster thrust the shutter open and closed it savagely. With pounding heart she crept over to the internal hatch and listened. But all she could hear was a faint, blurred buzz of voices and she could make out nothing at all of what was being said.

A m.u.f.fled groan from the bunk made her jump. She had temporarily forgotten all about her secret during the ordeal with the alien. After a struggle, she finally managed to close the internal hatch partially. Then she ran to the bunk and pulled the blanket aside. Barbara's lacerated face stared up at her with dazed and frightened eyes. Barbara tried to say something, but Vicki put her hand over Barbara's mouth.

'Koquillion saw me helping you,' she whispered accusingly, as if she were blaming the bewildered stranger.

'I knew it was stupid to try... I knew he would find out...

Koquillion knows everthing... Everything...' Overcome with panic, Vicki clutched Barbara's hand convulsively and bowed her head, tears starting in her big terrified eyes.

Still groggy with shock and the effects of concussion, Barbara neverthless tried to sit up. 'Who is Cowkwildion?'

she asked in a muddled but loudish voice.

Vicki put her hand back over Barbara's mouth, trembling with dismay at her outburst. 'Quiet! He'll hear you!'

In spite of the consequences of her appalling experience up on the ridge, Barbara quickly sized up the situation and redoubled her efforts to get up from the bunk.