'All the comforts of home, eh?'

She passed Ian a kind of natural stone bowl, and he sipped the water thirstily. 'I don't think I'll bother with the meat.'

'I shouldn't,' said Barbara. 'It isn't very nice.' Ian looked at the Doctor, who sat gazing blankly into the fire. He looked tired and dispirited.

They heard movement from the back of the cave.

Za appeared from the gloom. He marched up to the fire and stood looking down at them. 'You have meat now.'

No one answered.

'The animal was strong and hard to kill, but I killed it. Now there is meat for all the Tribe. The meat is good.'

More silence.

'They have brought you fruit and water in a hollow stone.' Za looked down. 'Is this the stone?'

'He's trying to make conversation,' thought Barbara hysterically.

Za seemed puzzled, almost hurt by their lack of response. 'Has anyone hurt you?'

The Doctor raised his head. 'When are you going to let us go?'

'You will stay here,' said Za flatly. 'I have the thing that you made, but I do not know if it will make fire for me. It will be best if your tribe and my Tribe join together - forever.'

'No,' shouted Ian angrily. 'We want to leave here!'

'Why? The cave is warm and dry. We will bring you food and water and wood to feed the fire. There is no better place on the other side of the mountains.' Menacingly, Za raised his axe. 'Do not try to leave here - or you will die!'

He turned and strode from the cave.

Ian found a sharp stick, speared a piece of meat, looked at it in disgust and pitched it into the fire, where it sizzled angrily.

The Doctor said moodily. 'Fire! Fire is still the answer, somehow, I'm sure of it. They revere it! If only we could use it to frighten them in some way.' He kicked moodily at a skull at his feet.

It rolled into the fire, sat there, grinning at him.

'Look at that skull, grandfather,' said Susan fearfully. 'It looks almost alive.'

Inside the empty eye-sockets of the skull, little flames flickered like glaring eyes.

Ian looked at the skull, and then jumped to his feet. 'Not alive, Susan - dead! Get me some pieces of wood, will you? We're going to make some torches - we can use the fat from the meat. Doctor, see if you can find me four skulls, not too badly bashed up.'

'What happens then?' asked Susan.

'Then to all intents and purposes, we're going to be dead. Just like that skull!'

Ian pointed to the fast-blackening skull in the heart of the fire.

The Tribe was having a great feast that night, sitting round the huge fire that roared at the mouth of the main cave. They crowded around it, roasting chunks of bloody meat on the end of sticks, thrusting them into their mouths when they were no more than charred. Children munched and played in the circle of firelight. Their mothers looked on, with no fear that the beasts from the forest would snatch them away.

Za sat in the place of honour, flanked by Hur on one side, Horg on the other. He looked proudly around his Tribe. They were warm, well fed, and safe - and he was their chief.

Suddenly there came a terrible cry of fear and a Tribesman ran into the circle of firelight.

Za jumped to his feet in anger. 'You were told to guard the strangers. Why are you here?'

The man was almost sobbing with fear. 'I was waiting outside the tunnel when I heard the stranger tribe calling me. There was a great wailing and shouting, so I crept to the end of the passage to look... There has been great magic, Za. You must come and see.'

'Show me,' ordered Za. 'The men will come with me, the rest stay here.' He ran towards the cave of skulls, Horg and the warriors at his heels. Hur ran after them.

The trembling guard led the way to the side entrance and pointed. He would go no further. Za marched into the little tunnel, followed by Hur, Horg and his warriors.

As they came into the cave, a horrifying sight met their eyes.

The stranger tribe had vanished. In their place hovered four gleaming skulls, flames burning from their eyes, and belching out from their mouths.

Horg fell to his knees in terror. 'The strangers have died! Their ghosts have come to punish us.'

The rest of the Tribe fell to their knees, wailing in fear.

Even Za stood frozen with terror, staring fixedly at the skulls.

In the shadows at the back of the cave, Ian whispered, 'Right, let's slip out now. Hurry!'

One by one they edged round behind the terrified Tribesmen, and down the tunnel that led to freedom. No one saw them - all eyes were on the four skulls. Seconds later, they were outside in the cold night air. Nearby they could see frightened figures huddled round the great fire outside the main cave. Keeping well away from the firelight, they ran into the forest.

One of the skull-bearing torches was almost burned away.

Suddenly it collapsed beneath the weight of its burden and the charred skull rolled almost to Za's feet.

The others leaped back in fear, but Za shouted, 'Look! This is nothing but fire and the bones of the dead!'

He snatched up one of the torches, shaking free the skull, and held it high, looking around the cave. 'The stranger tribe have gone.

While we looked at their fire and cried with terror before dead bones, they have gone!'

'They have gone into the night,' said Hur. 'The dark will hide them.'

Za waved his torch in a flaming circle. 'With fire, night is day,'

he said grimly. 'Bring fire all of you. We shall hunt them down!'

He led the way outside the cave and selected a band of his best warriors. Armed with blazing torches, the hunters set off at a run.

Ian led his little party through the forest at top speed. This time no one had any difficulty in keeping up. Even the Doctor didn't demand that they stop and rest.

They fled blindly through the darkness, and Ian hoped desperately that they were still on the right path.

It was with a feeling of enormous relief that he led them at last into the clearing where Za had fought the tiger. 'Nearly there,' he gasped.

They heard fierce yells behind them, and turning round they saw the gleam of fiery torches through the trees.

'Quick,' yelled Ian. 'They're right behind us! Run!'

They forced their way out of the forest at a stumbling run, bursting through the screen of bushes, and out onto the sandy plain.

The going was easier now, and a few more minutes brought them to the TARDIS.

Ian collapsed against the door, and turned to the Doctor, who was bringing up the rear. 'Hurry, Doctor, let us in. They'll be here any minute!'

The Doctor staggered up, fumbled for the key with agonising slowness, got the door open at last, and tumbled inside.

Ian ushered Barbara and Susan through the door, and turned for a last look behind him. He saw Za and his warriors burst out of the forest and onto the plain. One of the warriors hurled a spear, which clattered against the TARDIS.

Ian dashed inside and the doors closed behind him. 'Come on, Doctor, get us out of here!'

The Doctor was already busy at the controls...

Za skidded to a halt in frustration, before the strange blue tree.

Za glared angrily at it. 'Smash it down,' he roared. He dashed at the strange object, axe raised high. The thing gave a strange wailing cry -

and disappeared. Everyone flung themselves to the ground in terror.

The thought came into Za's terrified mind that he had been wrong -

surely the strangers did come from Orb after all.

It was some time later. Rested and refreshed, Ian and Barbara and Susan watched the Doctor anxiously as he hovered over the controls, making a rapid series of adjustments.