Oh, why didn't I listen to Partil? I could have arranged for the Doctor and Sam to be... removed. Then I wouldn't have had to think about it any more. I wouldn't be responsible.

'My name is Tvan Mauvril,' said the armoured Tractite. 'I command the Fifth Resistance Division. What's your name and area?'

'I'm Kitig. From Paratractis.'

'Paratractis? That doesn't ' A pause. A blink of night eyes. 'How did you get here?'

'Ah, only I can explain that properly.' The Doctor's voice again. 'There's a problem with the time lines, you see '

'Shut up, human!' snapped Mauvril. 'You're not in the Empire now.'

'I'm not human and I don't approve of the Empire any more than you do.'

Kitig rolled upright: there was a rustle of metal as he moved, and he saw four more of the armoured Tractites, two with guns levelled at him. The other two were holding the Doctor, an arm each.

'You'd better explain who I am,' said the Doctor with a smile. 'And I think Mauvril here would like it to be the truth, or these two people are going to walk off in opposite directions, each of them taking half of me away.'

Kitig looked at the hard eyes of the two Tractites holding the Doctor, smelled the hard smells. He turned to Mauvril.

'This is uncivilised behaviour! How can you make threats like this? How can you use weapons on us?'

Mauvril blinked open her night eyes. 'You're here,' she pointed out. 'With a human. That's a serious threat to us.'

'He isn't human,' said Kitig. 'We're here because his time machine malfunctioned.'

'Are there any more of you?'

'No,' said Kitig.

'Yes,' said the Doctor. 'But they're in a different location in space-time. You haven't got a chance of finding them, and it's no good making threats because neither Kitig nor I know where they are at the moment.'

'Then it's clear enough that neither of you has any useful information,' said Mauvril. She turned to the Tractites holding the guns. 'Kill them both. Quickly, no torture.'

'Wait!' yelled the Doctor.

Mauvril turned to face him, her body exuding a faint smell of anticipation. 'Does that mean you do have something useful to say to us? Or is it just that you don't want to die?'

'There's more at stake than my life or yours.'

'That's true.'

'More even than all the lives of all the Tractites and humans that ever lived.'

'So you are human.'

'No, not exactly, but that doesn't matter. What does matter is the effect that your experiment in altering history is having on the structure of the multiverse. You have to realise that this little piece of Africa and another piece about a million years down the timeline are the only bits of reality left at the moment.'

Mauvril turned to Kitig. 'What is this nonsense?'

Kitig met the alien Tractite's eyes. 'There may be some truth in it, Tvan Mauvril,' he said carefully. 'It bears investiga-tion. I swear on the honour of the Keeping.'

'The honour of what?' Mauvril's eyes swung from one to the other of them. 'Are you both insane?'

'No,' said the Doctor. 'It's just that the truth is a bit more complicated than you're prepared to accept at the moment.'

Mauvril pulled a long, black, ugly weapon from a holster strapped across her back.

'Tell me the truth, then,' she said, putting the barrel of the gun against Kitig's face. 'Tell me all of it. Then I'll decide what to do with you.'

Kitig swallowed. 'Very well. I come from a world called Paratractis. It's like Tractis. A peaceful place. But at the moment it's one of two alternative futures. In the other one, the humans survive and...' He hesitated, looked at the Doctor, who shook his head. Kitig took a breath, looked away from the Doctor and into Tvan Mauvril's eyes. 'The humans destroy Tractis in the other future. They destroy our people. And a small remnant go back into the past and make Paratractis happen by destroying the humans before they evolve. The Doctor is trying to prevent it, because he favours the humans. At least, this is what it says in the Book of Keeping Book of Keeping. But the Doctor '

'Good,' snapped Mauvril. 'That's all I need to know.' She turned to the Tractites holding the Doctor. 'Take him to the base.'

'Well done, Kitig,' said the Doctor, his voice heavy with irony. 'That should have just about made sure that none of us lives to see the morning.'

'I told the truth,' said Kitig.

'Yes, you told half the truth to an angry maniac who has the fate of everything that has ever existed or will ever exist straight in the sights of her blaster and her finger on the trigger. Next time, Kitig if there is a next time, which I really don't think in these circumstances there will be please do me a favour and try to tell a lie.'

The last word turned into a gasp of surprise as the armoured Tractites wrenched the Doctor off his feet. One flung him across her back, and both started out at a canter through the long grass around the shore of the lake.

Mauvril gestured with the gun. 'Kitig of Paratractis, you will come with us as well.'

Reluctantly, Kitig set off after the others, with Mauvril at his back. The grass whipped at his legs, and insects buzzed around him, disturbed by the movement. In the distance, he saw antelope galloping away, already taking fright at the approach of the huge, dark Tractites.

Were these armoured thugs really responsible for the creation of Paratractis? Was it right to let them destroy innocent primitives, just because they might one day evolve into humans?

Or was the Doctor right? Was 'everything that has ever existed or will ever exist' really under threat? Or was the Doctor lying, to protect his interests?

The questions hammered at the inside of his head, refusing easy answers. It was so hard to decide. If only he could decide, then surely everything would be all right.

Surely he would be able to go home.

The habiline settlement was in a narrow gorge cut into the base of the mountain. It was bigger, and better organised, than Sam had imagined: she quickly realised that Axeman's group of a dozen or so were no more than a hunting and foraging party. On the steep slopes of the gorge there were several dozen shelters made from sticks and crudely woven matting, built on ledges or at the entrances to small caves. The shelters looked too crude and temporary to be called houses, but they were certainly more than nests.

Inside the shelters, habilines lay on piles of dry grass and leaves. Most were already asleep, but they looked up sharply as Sam arrived, eyes glinting. Several got up and vaulted down the slopes towards her. Axeman and the others made signs which translated variously as 'our people' and 'others not dangerous'.

This didn't seem to have much effect. A habiline woman pointed at Sam, screaming. 'Dangerous!' came the rather unnecessary translation.

Other women started jumping up and down. 'Not our people! Dangerous! Children here! Take them away!'

Sam saw Axeman looking at her, frowning. She didn't for a moment believe that he or any of the males would defend her against their own people. She was going to have to act quickly or the tribe were going to rip her and Jacob apart. She clapped her hands together, looked around at the screaming habilines.

'I won't hurt you. I won't hurt your children. I'm here to help you.'

The screams subsided.

One of the women stepped forward until she was within spitting distance of Sam. 'You know our signs. You are kin of any here?'

Sam thought for a moment. 'I'm umm granddaughter.'

The habiline put her hands on her hips, a gesture so startlingly human that it was almost funny coming from the naked, hairy, upright ape.

'Daughter of who?' She raised her hands in the air. 'Whose daughter is this?'

Again Sam had to think. Evidently the distinction between 'granddaughter' and 'daughter' had been lost in the translation.

There was no telling how much of anything she said they were going to understand. And if she said the wrong thing...

The habiline woman was still staring at her.

'All of you,' said Sam at last. 'I'm the last daughter of all of you.'

'Liar!' snapped the habiline. 'Youngest daughter ' she gestured behind her, and Sam saw another habiline suckling a baby.

One of the crowd started jumping up and down and hooting. 'Danger! Danger! Kill! Kill! Kill!'

'Not daughter,' put in Axeman helpfully. 'Friend.'

'Not friend!' snapped the senior habiline woman, turning her gaze on the hunter. Sam decided to call her the Mother Superior. 'Not human.'

'I need your help to stay alive, so that I can help you,' said Sam, crossing her fingers and hoping that the Mother Superior could cope with a concept like that.

The habiline's eyes met hers, and the dark, semi-human face creased in a frown. 'Help people? What help people?'

'I have...' She gestured at Jacob. ' We We have umm healing stuff. Against disease. There was an accident. A mistake. have umm healing stuff. Against disease. There was an accident. A mistake.

One hunter got hurt.'

Sam realised she was babbling. Worse, she was babbling in pidgin English. The habiline watched her, with folded arms.

'We don't mean any harm,' concluded Sam desperately.

The habiline frowned, poked at the ground with a foot. 'You sleep in rocks,' she said finally, then turned her back.

And that seemed to be all there was to it. Sam heard a few echoes of the word 'rocks', then silence, apart from the muffled wailing of a baby.

'I keep watch,' said Axeman suddenly, and led the way back, beyond the shelters, to a place where the gorge ended in a dry, steep slope covered with pebbles. At the bottom of the slope, there was a jumble of broken rock.

'We're meant to sleep here here?' asked Jacob indignantly.

'Not sleep yet,' said Axeman. 'Water.'

The mention of the word immediately made Sam realise how thirsty she was. There were still a few swallows of water in the bottle in her backpack, but if the habs had some here...

Axeman was leading the way across the rocks. Suddenly he stepped down, and seemed to vanish.

Following, Sam saw a crevice in the rock, and at the same moment heard splashing noises. She pushed her body through the crevice, found a cave no, not quite a cave: she could see evening sunlight seeping in through cracks in the walls.

A glint of water.

A hand grasped hers: Axeman. He led her across what felt like pebbles, until she splashed into cold water.

Axeman let go, and she heard water moving, drinking noises. She bent down, cautiously cupped her hands and brought some water to her lips.

It smelled clean. It tasted clean. It obviously didn't do the habs any harm.

Sam took the risk and drank it.

She bent down, scooped up more water, drank again. Her eyes were beginning to adapt to the darkness: she could just make out the shadows of the habs crouched around the water, glints of moonlight on rock, dark blotches that might be moss.

A hand touched her left breast.

She jumped back, aware of a sudden silence in the cave.

The hand touched her again. Grasped.

Sam began to shake. How the hell do you tell a two-million-year-old apeman that he's really not your type?

Well, try the usual way.

'No,' she said firmly, pushing the hand away.

Silence. Then a flurry of movement, the sound of a fist hitting flesh, and a single, loud grunt: 'Leave!'

Habiline hoots and grunts filled the cave, turning into screams, splashes. Several heavy bodies pushed past her, heading towards the entrance.

Gradually things settled down again, but Sam's body was still shaking.

Cope with it, she told herself fiercely. Their manners might be two million years out of date, but they're still human males, or nearly human anyway. And they're not all the same: at least one of the others Axeman, probably defended me.

Slowly, cautiously, she backed out of the cave.

She almost collided with Jacob at the entrance, and jumped with shock. 'What's going on in there?' he asked.

'One of the habs made a pass at me,' said Sam. She grinned.

Jacob stared. 'Are you sure?'

Sam thought about it. Maybe the guy had just been curious, had wanted to know if she felt the same as his sort of woman.