The Doctor leaned over her, extended a hand with two tiny pale blue tablets in it. 'Antiviral,' he explained. 'To keep you going until we get to the TARDIS.'

Rowenna took the tablets, and immediately began to feel better.

'Where is this... TARDIS?' asked Julie.

'Oh, not far.'

'What about Jo?' asked Rowenna. 'She went off to '

'You mean she's here here?' The expression on the Doctor's face changed to one of delight. 'Oh, how wonderful! I've been wondering how she was getting along! How old is Matthew now? Is he at university yet?'

'Whoa! Hold on!' Rowenna was giggling again, helplessly. 'I only met Jo for two minutes this morning. The last time I met her before that was nearly five years ago. As far as I know Matthew's just started high school she says she hasn't seen you for twenty years.'

The Doctor rubbed his chin. 'More like three hundred. Where is Jo now, anyway?'

Julie was staring from one to the other of them. 'Hey! Let me in on this sometime, won't you?'

'Jo went looking for water,' Rowenna explained to the Doctor, ignoring her friend. 'We can't just pack up and leave.'

The Doctor sat down in the grass, drew his knees up to his chest and folded his arms over them. 'Then we'll wait for her,'

he said. He looked down at his hands, saw the hypodermic, still with Julie's blood in it. He pulled a thing that looked like a green rubber tennis ball from his pocket and fitted the hypo to it. It started to expand and contract slowly, almost as if it were breathing.

'May as well start work on a proper antidote while we're waiting,' said the Doctor. 'Does anybody know any good African campfire songs?'

The scents are changing.

Kitig remembered Partil's warning, in the library at home. It seemed so long ago; hard to believe it was only yesterday.

He tasted the air with his tongue, picking up the strange tones, the barely readable notes of this alternative reality.

He was fairly sure that he was still on Paratractis. The fundamental planet smell was the same, the deep rock, the salt oceans, the faint tang of polar ice. But the soft, pervasive scent of Tractite plants was gone. So was the sense of order, the visible glittering points of the orbital stations, the gentle touch of the pheromone relay net telling him where he was.

Here there was only emptiness. True wilderness.

A volcano towered in the distance, blue-tinted, shrouded in snow. There was a whiff of that snow in the dry wind, over-laid with the green things that lived on the slopes, and the hot acrid stench of a soda lake. Nearer, a series of rocky outcrops ended in a hill which tasted of slate, the hot dry rock baking in the sun.

And all around, the scent of the plains animals, their dung, their saliva, their exhalations, and the dry, crackling scent of the grass they ate.

Somewhere, water. Kitig realised that he was thirsty.

The Doctor's scent was strong, an alien track across the dry ground. It hovered in the air, visible, talking in alien voices.

Soothing voices. Kind voices.

I can't kill this being. He smells of virtue.

No. That had been a long time ago, on a different world, a world of libraries and ordered pheromones. The world that might have ceased to exist for ever, because of Kitig's own stupid indecision.

Narunil had been right. He was not suited for the trust he had been given. He had too many doubts, needed to think too much before acting.

But Kitig knew he had no choice now, whatever his reservations. He had his duty to his world, to his people, to his family. He had to carry out that duty whether he was suited to it or not. He would have to stop the Doctor, even if he did smell of virtue. And if that meant hurting him, Kitig knew he would have to do that, too.

He didn't want to think about what 'hurting' might mean in this context. He would do whatever it came to him to do. And live with the consequences.

He increased his pace to a canter, following the bright, easy scent across the grassland towards his target.

Jacob crouched down and watched the three of them singing under the time tree, hiding himself as well as he could in the tall grass.

He'd known it as soon as the Doctor had arrived. Despite his weird nineteenth-century costume, he had the air of a man from the Golden Age. The bright eyes, the brown-to-golden hair, the confidence. This was the future of humanity. And he had come to stop Jacob, to stop the Tractites.

I should have known it was too easy, he thought. I should have known it couldn't be possible that my dreams would really come true. Alien visitors who needed a helping hand to remove the human race from the face of the Earth. It's ridiculous. It couldn't possibly be that simple. Of course the human race is going to fight back. And here's this Doctor, making the first moves.

Jacob crouched down further into the grass, his whole body shaking.

He knew what the future humans were capable of. The death, the darkness, the destruction that came everywhere that Earth spread its empire. He knew that the Doctor's golden image was no more than an illusion: once the man found out what was happening, he would put a stop to it.

He would probably kill Jacob, too.

Alpha and Omega. The end of all things. But not for the whole human race; just for Jacob.

He closed his eyes.

No. He wasn't going to allow it to happen. He had planned this: and he was going to carry it through. He wasn't going to allow it to happen. He had planned this: and he was going to carry it through.

The original plan had been to use the whole UNIT platoon infect them, spread them out among the habilines, let them die and spread the virus. Now he was going to have to do all the infecting on his own and he was going to need a sample of the virus to do it.

He got up, ran crouching through the grass. On the other side of the time tree, antelope stirred nervously. But the Doctor and the two women were still singing, apparently oblivious of his presence.

I am the lion, he thought. I am the wolf. I am the sabre-toothed tiger. I can do this.

He slipped the knife out of his inside pocket, got up, pounced forward. He saw the Doctor's eyes, startled, then angry.

Felt the force of the man's will.

I am the predator Jacob dived for the hypo of blood at the Doctor's feet. He lifted it and the tennis-ball-like object it was attached to, at the same time slashing one of the women with the knife. He heard a satisfying scream of pain, felt blood splash on his arm.

Then he was turning, running, running crouched through the long grass. Behind him there was a single gunshot, then a man's voice. 'No!'

Jacob just kept on running. He found a rough trail in the grass, recently beaten down, and followed it towards the mountain.

He could hide out there until the Doctor got tired of looking for him.

Then he would find his ancestors.

And kill them.

Kitig heard the percussive sound, the human shouts, and stopped at once. He stared around him in the rippling heat of the afternoon. He saw a thorn tree and two low bushes growing on the rim of a dry river bed. An outcrop of rocks. He could smell the Doctor's nearness.

He waited, heard more shouts, saw a bipedal form moving through the grass. He started towards it at a steady canter, feeling the loose ropes that had held the Doctor's basket dance against his flank.

As he got closer, he saw that the biped wasn't the Doctor, but another human. The human shouted at him: 'Gavril!

Gavril! Stop him!'

Kitig stared, wondering who Gavril was, if there was another Tractite here, whom he was supposed to stop: then he saw the Doctor running through the grass, covering the ground at a truly fantastic speed for a biped, and gaining on the other human rapidly.

Kitig assessed the situation for a moment, judged the distance to the running figure, then he crouched down in the grass and waited.

The first human got the point. He changed course, led the Doctor along the dry river bed below Kitig.

Kitig watched him run past, watched the Doctor approach.

At the right moment, he jumped. It was easy, like playing a game in the garden.

He landed on the Doctor.

The apelike being had tried to dodge sideways, had almost made it: but not quite. He was caught, lying flat in the belly of the dry river, his chest under one of Kitig's front hooves. A single stone rolled across the dusty ground, settled against the gnarled root of a long-dead tree.

Kitig leaned forward, felt the alien's ribcage bend under his weight. The Doctor's eyes bulged outward, his face flushed with blood.

'You don't ' he gasped. 'Don't want to '

'I don't want to, but I have to,' said Kitig.

But at the same time he lifted his leg slightly, easing the pressure on the Doctor's chest.

'There won't be anywhere to go back to, Kitig,' gabbled the Doctor. He took a heaving breath, went on, 'No home, no family, no nothing.' Another breath. 'Everything will cease to exist.' Another. 'You have have to believe me.' to believe me.'

His eyes locked on to Kitig's. Kitig felt himself being persuaded. That was the danger of the Doctor, he thought: his ability to make you think he was right right.

'No one can own the only road to virtue, or hold the only key to truth,' said Kitig, more to himself than to the alien.

'Bessarinil, from the Vargukonon Vargukonon,' commented the Doctor. He was breathing more easily now. ' "Because there is more than one road, and more than one key". But that just isn't true this time. We're not talking about comparative philosophy: this is temporal physics, and you can't '

Kitig lowered his hoof to the Doctor's chest again, then hesitated, trembling. He felt the heat of the sun branding the back of his neck.

This is a sentient being.

'We should be working together to solve this problem, Kitig. You're rational, merciful, civilised surely you can see that there must be a way '

He broke off, quite suddenly, his face darkening.

'Except that there isn't,' said Kitig, softly, a horrible certainty forming in his mind. 'There's no way out, is there, Doctor?'

He raised his free front hoof, ready to bring it down on the Doctor's head, and end his life with as much mercy as he could.

CHAPTER 15.

Julie was unconscious, the blood from the wound that Hynes had made in her arm pooling around her, soaking into the hard earth.

Rowenna had shuffled as close as she could, doing her best to ignore the blaze of agony from her back every time she moved. She'd found the cuff the Doctor had used and had applied it in an effort to stop the bleeding.

It wasn't a great success: the wound was too deep, she couldn't get the cuff tight enough.

She watched Julie's life seep out with a growing sense of panic.

Doctor, where are you?

Perhaps Jacob had got him. Perhaps the crazy son of a bitch would be back here in a minute...

She scrambled around under the time tree, cursing her useless legs, searching for the gun.

Then she saw the dog.

It was keeping its distance, watching her from the grass outside the shadow of the tree. It was lightly built, its coat almost the same pale brown as the baked earth.

'Shoo!' snapped Rowenna.

The dog growled.

Another dog appeared by its side.

Rowenna felt her heart rate increase. She looked around for something to throw, but there was only the grass and earth.

She scrabbled around in the crushed grass, found a plastic strap.

It was attached to a bag: Julie's bag. She remembered Jo taking the organiser from it, a half-hour ago.

A world away.

She picked the bag up, shook it, heard small change rattling inside.

Coins, she thought. I can throw them.

There were three dogs now, and they were advancing steadily, tails wagging. But Rowenna doubted they were about to become friendly. She poured out the contents of the bag. Two quarters, a couple of dimes, some Tanzanian small change.

She flung one of the quarters.