The Doctor sat cross-legged on the ground, surrounded by a litter of his possessions, examining a moss-covered pebble with absorbed attention. Fishing in his pockets, he produced a curved Meerschaum pipe and a big box of old-fashioned matches.

From his hiding place in the rocks, Kal watched the activities of the stranger with fascination. He leaned forward curiously as the creature produced mysterious objects from beneath its skins. The creature fumbled with one of the objects - and Kal saw a miracle!

Grasping his stone-headed axe, he rose and padded silently towards his prey.

'Grandfather!' called Susan again. 'Grandfather!'

From somewhere in the distance, there came a cry of pain, a yell of triumph - then silence.

'It came from over that way,' said Ian. 'Come on!' They ran towards the sound.

It didn't take them long to find the rocky enclosure. The Doctor's old fur hat lay on the ground. Beside it, was his pipe, and his notebook. Of the Doctor himself there was no sign.

'Grandfather!' screamed Susan. 'What's happened?'

'Don't panic, Susan,' said Ian sharply.

Susan began scrambling up the side of the nearest boulder 'I must find him. Maybe I can see from up here.'

'All right, but be careful.'

'Look, Ian,' whispered Barbara. She pointed.

The Geiger counter lay at their feet. Its glass was smashed.

Ian picked it up and examined it. 'That's no good any more!'

'Maybe he saw something interesting,' suggested Barbara uneasily. 'Perhaps he just rushed off to investigate?'

Ian picked up the Doctor's pipe. 'Dropping this?'

'What do you think happened, then?'

'Well, I suppose he could have seen something and got excited and gone after it,' said Ian slowly. 'On the other hand, he could have been - taken. That yell didn't just sound like excitement.'

Susan jumped down from her rock. 'I can't see anything.

There's not a sign of him anywhere.' She looked in anguish at Ian and Barbara. 'Something's happened to him, I know it has. We've got to find him.'

Her tone was close to hysteria, and Barbara said, 'Calm down, Susan, it won't help to panic.'

Susan wasn't listening. She stooped down and picked up the notebook. 'He's left his notes!'

'He seems to have left quite a few things lying about,' said Ian.

'Hat, pipe, notebook, Geiger counter...'

'He may just have laid them all down and gone off somewhere,' suggested Barbara, more to console Susan than because she believed it herself.

Susan shook her head vigorously. 'No, no, no. Grandfather would never have left his notebook, it's vital to him. It's got the key codes to some of the machines in the ship, and notes about places we've visited. He simply wouldn't go off and leave it. Please, we must go and look for him. Something's happened, I know it has.'

'We'll find him,' said Barbara soothingly. 'He can't be far away.'

'What did you see on the other side of the rocks, Susan?' asked Ian.

'Just a line of trees. I think it was the beginning of the forest.

There was a sort of gap between them, it looked like a path.'

'All right. We'll try there first.' Ian stowed the Doctor's possessions away in his pockets, putting the broken Geiger counter back on the sand. As he put it down, he paused for a moment, patting the sand with the flat of his hand.

Barbara looked on curiously. 'What is it?'

'This sand. It's cold. Almost freezing.'

Ian straightened up, and led the way round the boulder.

Inside the cave of the Tribe, Hur watched anxiously as Za laboured vainly with his little pile of charred sticks. Beside him the burly, grey-bearded figure of Horg, Hur's father, watched Za's efforts with a sceptical eye. 'Kal says that in the land he comes from, he was a chief, and often made fire.'

'Kal is a liar!'

'Kal says he has travelled far from his own lands and he has forgotten how fire is made. He says that soon Orb, the sun, will remind him how it is done, and he will make fire for all of us.'

'All of Kal's tribe perished in the last great cold,' said Za furiously. 'If he had not found us, he would have died too!'

'What else did Kal say?' asked Hur.

'He says Orb will only tell the secret of the fire to the leader.'

'I am the leader,' grunted Za. 'Orb will tell me.' He stared moodily at the grey ashes. 'I am the son of the chief, the great firemaker. Even though he did not show me how to put flame into the sticks, I shall soon discover the secret for myself.' Za smote himself on the chest with one huge fist. 'Kal came, and I did not kill him. I let him eat with us, and sleep in our caves.' Za's voice rose to an angry roar. 'Must I spill blood to make the people bow to me?'

Excited shouts came from outside the cave. 'It is Kal! Kal comes!'

'Kal brings us his kill!'

Za snatched up his stone-headed axe and ran from the cave, Horg and Hur close behind him.

Outside they saw Kal, surrounded by a crowd of excited Tribesmen. He bore some strange creature across his shoulders and, as they watched, he dumped it down on the flat-topped rock outside the cave.

Curiously the Tribe gathered round, jabbering with excitement.

Za shoved his way through the crowd and looked down at the unconscious figure on the stone. 'This is a strange creature. Why do you bring it here, Kal? Is it good to eat?'

Kal glared challengingly at him, his bearded face alight with triumph. 'Is Za, son of the great firemaker, afraid of an old man?'

'No. Za fears nothing,' said Za, and prodded the old man's body with his foot.

'When will Za make fire come out of his hands?' 'When Orb decides it.'

Kal laughed. 'Orb is for strong men. Men who can make Orb obey their will.' He pointed dramatically at the body on the rock. 'Orb has sent me this creature as a sign of his favour. This old one can make fire come out of his fingers!'

There was an awe-stricken murmur from the Tribe.

'I have seen it!' shouted Kal. 'He is full of fire inside. The smoke comes out of his mouth.'

'As lies come out of yours,' sneered Za. He leaned forward and poked the body with his finger. 'It is only an old man wearing strange skins.' The Doctor groaned suddenly, and Za leaped back.

Kal was quick to seize his advantage. 'Za is afraid of the creature. Kal was not afraid. A strange tree came, and the creature was in it. Za would have run away if he had seen it, but I watched and followed!'

With an angry roar Za leaped for Kal.

Kal dodged aside and leapt upon the rock. 'Hear me!'

'Let him speak!' shouted Horg, and Za drew back.

'I saw this creature make fire come out of his fingers,' shouted Kal. 'I remembered Za, son of the firemaker. When the great cold comes again, you will all die if you wait for Za to make fire for you, but I, Kal, am a true leader!' Kal pointed down at his captive. 'We fought together like the tiger and the bear. When he saw that my strength was too much for him, he lay down to sleep. I, Kal, carried him here to make fire for you!'

There was a roar of approval.

'Why do you listen to Kal's lies?' shouted Za. Horg said, 'Za has many good skins. Perhaps he has forgotten what the cold is like.'

'Tomorrow I will kill many bears for the Tribe,' shouted Za.

'You shall all have warm skins!'

Horg said drily. 'I think tomorrow you will still be here, rubbing your hands together and holding them to the dry sticks and asking Orb to send you fire - and the bears will stay warm in their own skins!'

There was a shout of mocking laughter.

'What I say I will do, I will do!' said Za.

'Hear me!' screamed Kal again. 'I say that the firemaker is dead! You are no firemaker, Za. All you can do is break dry sticks with your hands. But I, Kal, will make them burn - and I shall be leader!'