'I know. Now it all depends on whether that bulkhead door can hold them.'

On the other side of the bulkhead, two of the Sea Devils were bringing up a bulbous-headed device, a kind of portable electronic cannon. At a gesture from Sauvix, they switched on the device and trained it on the door.

There was a steady hum of power. Slowly, very slowly, the surface of the ma.s.sive metal bulkhead began to char and crumble.

For the moment at least there was no sign of this on the other side. Vorshak and his men were able to s.n.a.t.c.h a few moments of much-needed rest. Medics appeared to tend the wounded, emergency rations were issued and suddenly Turlough came running up, blaster-rifle in hand.

'The Doctor and Tegan...' he gasped. 'Where are they?'

Vorshak looked grimly at him. 'So, there you are.'

Turlough had an uneasy feeling that the Commander was wondering whether to have him shot now or wait till later.

'Your friends are alive,' said Vorshak at last. 'At least for the moment. The Doctor's gone off to see if he can do something to stop this Myrka creature.' Vorshak smiled grimly. 'You might say that the Doctor is contributing to the defence of the Base just as you are.'

'I'm sorry?' said Turlough politely.

'You are volunteering your services to defend this bulkhead. Isn't he, Bulic?'

Bulic nodded, his face grim. 'That's right. We appreciate it very much. Now get over there with those guards in the front!'

Turlough looked at them in horror. He'd been acting with unusual bravery but only to try and help the Doctor and Tegan. The last thing he'd ever wanted was a hero's death. But it looked as if he was going to get one all the same.

8.

Sabotage Lieutenant Preston was following the Doctor and Tegan along the corridor when there came a bleep from her communicator. She stopped to answer it. 'Lieutenant Preston here.'

The strained voice of a guard came over the intercom.

'The monster it's in corridor seven.'

'Try to hold it back as long as you can.'

'We'll do our best,' said the voice dubiously. 'But I wouldn't bank on it!'

The intercom flicked off.

The Doctor paused, trying to chart the Myrka's progress from his sketchy knowledge of the layout of the Base. 'It entered by airlock one, now it's in corridor seven. It must be making for somewhere...'

'It seems to be heading for the Bridge,' said Preston.

'Yes, that would be it. The Bridge!'

Lieutenant Preston reached for her communicator. 'I must warn them...'

'Later,' said the Doctor impatiently. 'Listen, do you have ultra-violet convertors on the Base?'

'Yes, I should think so. There are some in the Solarium.'

The Solarium was one of the Base's recreational facilities, a cunningly designed area where you could lounge beneath plastic palm trees on a simulated beach, against a back projection of tropical sea and sky bathed, of course, in artificial suns.h.i.+ne. It was designed to counteract the effect of long spells of undersea duty. It was said you could even get a tan if you stayed in there long enough, though few people bothered.

The Doctor was thinking hard. 'Good. Now, will the Myrka need to pa.s.s this way on its route to the Bridge?'

'From corridor seven? Yes, this is the main access corridor.'

'Perfect. I'll need the ultra-violet convertor brought here immediately please.'

Giving him a puzzled look, Preston switched on her communicator. 'Lieutenant Preston to tech. unit. Send a squad to the Solarium, dismantle the UV convertor and bring it to the junction of corridor one and the main access corridor. This is an emergency, priority one.'

The edges of the bulkhead door were charring and smoking like burnt toast, thought Turlough. Nostalgically he remembered the ritual of study-teas at his public school, with a terrified f.a.g to make the toast. He looked at the blaster in his hand and wondered what he was doing here.

Bulic stared at the bulkhead. 'It won't hold much longer.'

Vorshak was deep in thought. 'There's only one thing for it. We'll have to break radio silence, call Sea Base Command and ask for help. We need more men, heavier weapons... But if we do break silence '

'Every enemy listening post will pinpoint our position,'

completed Bulic.

'It seems we lose either way. But there's no alternative.

The way things are going, this Base could fall into those creatures' hands. Our people have got to know!'

On the other side of the door, Vorshak's opposite number, Sauvix, Commander of the Sea Devils, watched the operation of the heat cannon with quiet satisfaction.

The cannon was one of the most impressive achievements of Silurian technology. It built up and focused an incredibly powerful heat-ray. The bulkhead door was made of specially reinforced steel, several feet thick. Under the influence of the heat cannon, it was crumbling like the wall of a sandcastle attacked by incoming waves.

Sauvix looked around his Warriors. They stood grouped around the door waiting. It would not be long now.

A couple of technicians came staggering along the corridor carrying the UV convertor, a bulky silver box packed with electronic equipment.

'There you are,' said the Doctor. 'Just set it up over here, would you? And if you'd be kind enough to lend me that tool kit?'

Unclipping the tool kit from his belt, the technician handed it to the Doctor.

'That will be all,' said Lieutenant Preston.

'Ma'am.' The technician saluted and hurried away, glad to be gone.

The Doctor removed the cover from an electrical junction box and began connecting up the UV convertor.

He looked up at Lieutenant Preston. 'What do you think?

Will the lighting circuit bear the maximum convertor load?'

She shrugged. 'Just about! I'd better keep watch.'

She moved along the corridor, keeping an eye out for the Myrka.

Tegan watched the Doctor for a moment. 'What does that thing do?'

'Converts normal lighting into ultra-violet.'

'What are you planning to do with it?'

'Oh, I just want to bring a little suns.h.i.+ne into the Myrka's life!'

Tegan gave him one of her long-suffering looks.

The guards were doing their best to delay the Myrka, but there was little hope of success.

Some of them tried the Doctor's trick of throwing power packs at the monster, but the trick wouldn't work for a second time. The Myrka was well aware of the danger by now. It turned its head, smas.h.i.+ng aside the power-packs with claws or tail, so that they exploded harmlessly away from its eyes. The guards could only fire their useless weapons and fall back as slowly as possible. Many died in the process, electrocuted by the energy field that crackled through the Myrka's body.

The Myrka continued its relentless progress towards the Bridge.

Controller Nilson was listening to Bulic's voice on the communicator. 'The Commander is on his way up to signal Sea Base Command. Have Maddox stand by for link-up.'

Like the firing of the missiles, direct communication with Sea Base Command was a process that could be authorised by the Commander alone. As a further precaution, it could only be done by computer link-up with an authorised synch-operator.

Doctor Solow gave Nilson an anxious look. With Maddox in his current condition, the work of sabotage still not complete, Vorshak's decision meant that they both risked discovery.

'What are we going to do?' she whispered.

Nilson considered the crisis with his usual icy calm.

'Maddox must finish the work that he has started,' he said with determination. 'Come with me.'

They moved towards the computer bay.

Lieutenant Preston was scanning the corridor ahead for signs of the Myrka. She turned and looked over her shoulder at the Doctor who was elbow-deep in electronic circuitry. 'I suppose you know what you're doing, Doctor?'

'The Myrka is a creature of the blackest depths,' said the Doctor thoughtfully. 'At least, it was until the Silurians started tinkering about with its biology. Anyway, it still has little tolerance of light and, I hope, none at all to ultra-violet rays.'

'Hope?' said Tegan suspiciously. 'Doctor, can you be sure this will work?'

'No, Tegan,' said the Doctor irritably. 'I can't give you any guarantees. Perhaps you'd prefer to ask it nicely to go away?'

Tegan sighed and shut up.

Maddox was still working at the same frantic speed when Nilson and Solow came into the computer bay.

Nilson nodded approvingly. 'The work goes well. He is almost finished. Doctor Solow, make your way to the escape pod and wait for me. I'll join you as soon as I can.'

'What about Maddox's conditioning tape?'

'Take it with you. It will provide our East Bloc colleagues with essential information.'

Doctor Solow nodded. 'As you wish,' she said wearily.

'Good luck.' Taking the disc from a locker drawer she hurried away, clutching it in her hand.

The Doctor was connecting circuits with desperate speed.

'Are you ready, Doctor?' called Preston.

Absorbed in his work, the Doctor didn't answer.

'Doctor,' said Tegan urgently. 'Are you ready yet?'

'Almost,' said the Doctor. 'Almost!' He went on with his work.

Doctor Solow came running down the corridor from the direction of the Bridge. She halted for a moment a the sight of the Doctor and Tegan, then ran on past them. The Doctor didn't even notice.

Tegan stared after Doctor Solow. 'Where's she off to in such a hurry?'

Lieutenant Preston looked up in surprise as Doctor Solow ran past her. 'Doctor Solow, come back,' she called.

'You mustn't go that way, it's too dangerous. The Myrka is coming...'

Doctor Solow ignored her. She ran round the corner, down more endless corridors, turned another corner and found herself facing the Myrka. It was too late to turn and run, and she flung herself forward, kicking out at the Myrka in an attempt to force her way past.

The attempt was doomed. The long tail lashed out and she was thrown across the corridor, her body glowing and crackling with energy. As she slumped dead to the ground, the programme disc rolled from her outstretched hand.

The Myrka moved on.

Minutes later a guard ran from the side corridor, pausing at the sight of Doctor Solow's body. He knelt by it for a moment, checking that she was dead. As he straightened up, his eye was caught by the programme disc lying against the wall. He bent to pick it up, studying the code stamped on the case. His eyes widened. '43Y?' It was the highest security cla.s.sification on the Base.

Slipping the disc in his pocket, he turned and ran back down the corridor.

As Icthar and his two fellow Silurians strode from the airlock, Sauvix and his Warriors raised their hands in salute. Icthar bowed his head, acknowledging the tribute.

'How goes the battle?' he asked.

'The outcome is certain,' said Sauvix proudly. 'The ape-primitives are no match for my Warriors. They will soon be crushed.'

Commander Vorshak hurried along on his way to the Bridge and stopped in astonishment at the sight of the Doctor.

'How is it going, Doctor? Do you have everything you need?'

'Oh yes, I think so,' said the Doctor cheerfully. 'It'll work, or it won't. We'll soon know. What's happened to Turlough, Commander?'