She rounded another sharp turn and slammed on the brakes. The Travco was stopped right across the road. There was a car backed up behind it, the driver already out and pulling open the Travco's doors. There was n.o.body inside.

Where was he? Hiding amongst the trees? She looked around, frantically. But the trees were naked, standing like narrow arms with a thousand fingers, nothing but open s.p.a.ce between them. He'd stand out like a crow on snow if he was there.

She had to find him and kill him, right now, right this minute. The question was, what range was safe? And how far could the Doctor's device reach less than fifty yards, but how much less?

'Luis,' she said, 'that man in the green shirt standing beside the campervan. I want him to come here.'

Luis turned his attention to the man, who was pacing up and down beside the open door of the Travco. The man's irritated walk didn't change. He slapped his hand against the wall of the vehicle.

Then this had a very short range indeed. Swan let the car roll forwards until she was within shouting distance of the man. 'Did you see the driver?' she called out.

The man pointed down the road, past the Travco. 'He took off like a rabbit out of a box,' he said. 'The law must be after him, that's all I can say.'

Swan backed up, aimed her car at the trees, and roared around the Travco, her tyres spitting half-frozen mud. She shot past a guard in a little white tollbooth, leaving him gaping.

'Up ahead,' said Luis.

Swan nearly crashed into a tree. She swung the wheel and screeched to a halt in an empty parking lot.

'What did you say?'

Luis's voice was low and gravely, as though he hadn't used it for years. 'Up ahead,' he murmured.

He could could sense the Doctor. Not close enough to kill, or he would have done it instantly. Oh perhaps Luis was sensing the Doctor's lethal device. One piece of technology picking up vibrations from its kin. sense the Doctor. Not close enough to kill, or he would have done it instantly. Oh perhaps Luis was sensing the Doctor's lethal device. One piece of technology picking up vibrations from its kin.

They were in Great Falls Park, and they had run out of road. 'Get out,' she told Luis, shutting off the engine. She grabbed the shotgun out of the back seat. The parking lot was next to a visitor's centre in an old tavern, and a ca.n.a.l that ran parallel to the Potomac River. 'In the house? Luis, is he in the house?'

Luis shook his head. He pointed vaguely across the ca.n.a.l, towards the river.

Swan took Luis by the hand and led him over the wooden bridge to the towpath on the other side. Water roared through the lock beneath their feet. 'He's trying to lead us away from other people,' she muttered. Their boots made a plasticky crunch on snow and red gravel. 'Very heroic. Remember, the moment you can do it, kill him'

Her head swung from side to side, waiting for the Doctor to spring out from somewhere even from the sluggish water of the ca.n.a.l. A pair of geese ran out of their way. UNSAFE ICE, warned a sign. A guy riding a bike glanced at them and sped away in panic.

Now Luis was leading her, his cool fingers still intertwined with hers. She understood now that there was nothing left of her friend; she was being pulled along by an alien, not a human. A machine built out of the ruins of Luis's brain, using his neurons for sc.r.a.p. There were so many things she needed to think about. What the Doctor had told her about the eggs. About whoever had come up with this technology in the first place. About what Luis was doing to her mind, to her brain. But she couldn't think about any of it now They had to get rid of the Doctor. And then they would go somewhere quiet, and she would be able to sort it all out.

A side path split away from the towpath. Luis didn't hesitate, turning onto a wooden bridge that crossed the first gush of the Potomac. He stopped partway across, turning his head slowly, like someone moving the aerial on top of a TV.

Maybe the rocks were getting in the way: everything here was stone, slashed and sliced and shattered by the water. It seethed beneath the bridge in patterns as complex as the static on a screen, forming miniature whirlpools, little channels, swirling backwaters.

Suddenly Luis was moving again. The bridge became a raised walkway across an island of grey rocks and grey trees.

There was no-one here. Swan wanted to stand still for a moment, to sit down and rest. Everything was lit up with winter sunshine, fresh and cold and clear, as though frozen in crystal. A single raptor drifted overhead, black wings spread wide. It folded itself into a tree as they ran by.

There was a second bridge, this time over a rocky gully where only a trickle ran through. 'Stop,' said Swan quietly.

Luis stopped in his tracks, staring intently up ahead.

'Wait here for one minute,' she murmured. 'Then follow me.'

She went forward. How far did the wooden trail lead? She could hear furious white noise ahead, the sound of the Great Falls. The Doctor was running out of dry land.

The trail ran out, suddenly, turning into a wide wooden platform on the edge of a cliff. There was a huge rock in the centre. Swan edged forward in case the Doctor might be crouching behind it, keeping the shotgun at the ready. But there was no-one here. Swan barely glanced at the Falls themselves, a gorge a hundred feet wide, a great flat expanse of rock being demolished by violent water.

He must have left the trail. The only cover was the boardwalk; everything else was raw trees and rocks tumbled like dice. But if he was down there, hidden by the wood, he couldn't see her. Come out, come out, wherever you are.

this was crossing the bridge behind her. She decided to move things along. She pointed the shotgun down at the planks and pulled the trigger.

Wooden, shrapnel and smoke exploded up around her. She dodged back, cursing, blinded for a moment by a rain of splinters. She batted them out of her face with her gloves.

The Doctor appeared from beneath the platform on the far side. He held a ball of plastic in his hand. He held a ball of plastic in his hand. He stared at her: where was Luis? Why weren't they together? In that split-second, Swan knew she had the drop on him. Behind her, Luis stepped up onto the platform. He stared at her: where was Luis? Why weren't they together? In that split-second, Swan knew she had the drop on him. Behind her, Luis stepped up onto the platform.

Look Ma top of the food chain!

' Do it Do it,' screamed Swan, but Luis already was.

It was like sticking your thumb into the torn wires at the back of an electric kettle. It was like jamming your head inside a bell and then striking it as hard as you could. It was like putting on headphones and pressing 'play' without realising the volume is turned all the way up. It was the feeling of the circuitry printed inside your head getting ready to shift and change.

There was a crucial instant, like the moment of unbalance on a tightrope, when the Doctor was about to fall. Mentally flailing for anything to grab onto, anything anything to focus on, anything to deflect the process that was taking root inside his skull. The more he tried to focus, to remember what he was supposed to do, the more it seemed to feed energy to that process. The roar of the falls and the winter sunlight grew into a blur like gravel in the eyes and ears. to focus on, anything to deflect the process that was taking root inside his skull. The more he tried to focus, to remember what he was supposed to do, the more it seemed to feed energy to that process. The roar of the falls and the winter sunlight grew into a blur like gravel in the eyes and ears.

He had fallen to his knees on the rocks, and in front of him were the contents of his pockets: coins and trinkets, transistors and toys. On a piece of paper there was a design drawn, its lines and curves carefully marked out in a pattern of geometric relationships and symbols. It was Bob's occult sigil, the diagram he had given the Doctor to protect him from whatever cosmic forces Swan might be able to yield.

And bless you, Bob, bless you, it didn't mean a thing.

In that split-second of distracting nonsense, the Doctor's thumb pressed into the trigger of the device.

120.

We waited for hours. Bob and Peri waited to see what was going to become of their lives. I waited to see how my book was going to end.

And then the door opened. The Doctor came through. His black suit was dusty and damp and one of the knees was torn.

Otherwise, he looked entirely undamaged.

'Doctor!' shouted Bob. The Doctor gave a little bow.

'You could have called!' said Peri, trying hard not to burst into tears.

'How do we know it's him?' I said.

The Doctor raised an eyebrow at me. 'Do I strike you as the somnambulistic victim of neural reprogramming?'

Peri hugged him. 'You are OK, aren't you?'

The Doctor nodded. He looked tired, but satisfied, like someone returning from a long day's good work.

Bob said, 'What about Swan? And Luis? What about the Savant? Is the Earth safe? What happened?'

'Well,' said the Doctor, 'I'll tell you.'

Mondy had continued monitoring Swan's calls the whole time.

He had overheard me setting up the meeting in the diner, and pa.s.sed it on to the Doctor. The moment the Doctor was finished at Swan's house, he put the pedal to the metal to try to catch us up. He knew the number of the payphone across the street because he'd been there five minutes ago. When he called me and then Swan at the payphone, he was just around the corner.

The police radio we had 'borrowed' let him broadcast a phony message about the roadblock on the bridge. (In fact, the slow traffic was quite normal. ) He had hoped to channel Swan's movements until she was as isolated as possible it hadn't been his plan to end up in a tourist attraction. But at least, in the depths of winter, there hadn't been that many people around.

The Doctor admitted, with a mixture of humility and grouch, that he had overestimated his own ability to withstand the Savant's mental onslaught. 'I deal with brainwashing and other such nonsense all the time,' he said, with a dismissive wave of his hand. 'This was different. It was far more invasive, far more physical. The more I fought, the more I thought thought, the more it was able to turn my own mind against me.

Bob's diagram bought me a moment of grace. For just an instant, I wasn't thinking at all.' Bob looked equal parts chuffed and puzzled, but he was happy to accept his role in saving the day.

Peri kept giving the Doctor hugs. She even made a cup of tea and brought it to him, while they both joked about it. She looked more relaxed than she had since I had first met her, and not only because the crisis was over: she had made up her mind about where she wanted to be.

We saw Mr Ghislain once more. The Doctor pulled some strings to get us access to the rest home where Swan and Luis had been placed for observation, and perhaps a few more so that I could come along for the visit. I don't know what strings he pulled to allow Mr Ghislain to bring his parrot.

I don't know for sure who Ghislain or the Eridani really were. I prefer my initial guess: Russian agents whose technology a supercomputer with organic components, possibly intended for s.p.a.ce exploration had got loose, perhaps after a deal with a double agent went sour.

Swan and Luis had been moved to a little patients' lounge for our visit. They sat side by side on a faded brown sofa, next to a shelf full of tattered paperbacks and National Geographics. They were a pair: both quite relaxed none of the stiffness of a victim of catatonia both staring at nothing.

Waiting for input, for instructions.

Mr Ghislain sat before them for a long time, consulting a device he held in his lap. His parrot perched inside its cage on top of the bookcase.

At last he said, 'Events have repeated themselves. At the moment you sent the interrupt signal to the Savant structures inside Mr Perez, it acted in self-defence by creating another copy of itself'

'I should have realised that would happen,' said the Doctor. 'Luis copied himself copied the Savant into Swan.'

Ghislain said, 'However, the interrupt signal then shut down the new Savant as well. Evidently it was unable to copy itself to your mind.'

The Doctor admitted, 'If I hadn't been distracted at the crucial moment by Bob's bit of scribble, I'd be sitting on that sofa beside them.'

'Is there hope for them?' I asked.

'We may be able to reverse some of the changes to their neural pathways,' said Ghislain. 'But I regret neither one will be restored to their original state. I propose you permit me to take them to our ship.'

'No,' said the Doctor.

'They can no longer function in this society. We offer to care for them.'

'And do a little experimentation at the same time? No, Ghislain. Do what you can for them, but they're not leaving Earth.'

'The Eridani regret this outcome.'

'Regret it? A successful test of your new weapon?'

snapped the Doctor. Ghislain looked at him placidly. 'The "supercomputer" these devices combined to create. It was a cuckoo's egg all along designed to infiltrate a society, no matter what technological level it might have achieved. It could adapt itself to any network, from a highly advanced computerised net to organic brain structures. Create a version of itself for any environment, and then spread itself like so much viral payload.'

'It is truthful that the slow package was unintended for Earth,' said Ghislain. His face was blank as ever, but his grammar was breaking down in the face of the Doctor's onslaught. I thought of Operation Sea-Spray, a biological warfare experiment in the early fifties. The Army sent aloft a bunch of balloons carrying a supposedly harmless bacterium, Serratia Serratia, then burst them over the Bay Area. That harmless little bug lodged itself in lungs throughout the city, causing a steep rise in pneumonia.

'Intended for a rebellious colony? Or any medium-tech civilisation that would gratefully accept your "gift"?' The Doctor planted his hands on his hips and loomed over Ghislain. 'I expect you not only to do your best to restore the minds of these people, but of all the people touched by your technology. Do you understand?'

I don't know what power the Doctor had over the 'Eridani': presumably he had threatened to expose them. But they seemed happy enough to do as they were told. And why not? Each victim they examined would render more valuable data on their trial.

The Doctor arranged for Ghislain (and his parrot) to visit Ritchie, and went along with them to keep an eye on things.

Ghislain brought yet another device, one that could unpick the mental knots left behind in the unknowing victims, snipping out the time bomb of hundreds of Savant programs nestled in nervous tissue, waiting to hatch.

They walked the streets for a day and a half, letting the device pick out men and women and children who had been affected, getting close enough to them to let it do the rest of its work. Ritchie's zombies knew no more about the cure than they did about falling ill. It wasn't perfect; the Doctor suspected a lot of people would be left with small, odd gaps In their memories, perhaps even occasional, minor speech or concentration difficulties. 'The small but noticeable scars of neurosurgery at a distance,' he said, with a mixture of sadness and sourness. But the job was done; in the end, there were only two people Ghislain couldn't restore to pretty much normal.

Once upon a time there was a young princess who lived by the seash.o.r.e. And G.o.d, her life was dull. She couldn't strap on armour and ride a chariot into battle, like her brothers the princes. She would never be a great king or a master sailor, just a prize to be fought over. She had nothing to do but sit in a field near the ocean, picking flowers with her ladies-in-waiting. Until one day they were approached by a huge white bull. The young women were badly frightened, but the princess knew she had found her ship, her chariot. She climbed on the back of that bull, ready to ride.

Maybe that's how the story goes.

So where are they now?

Bob's out there riding the new frontier. 'Power,' he explains, 'is something you can borrow. The alchemists knew it. The first cavemen who stuck horns on their heads were trying to borrow the power of the animals.' He knows from first-hand experience as sysop that the law isn't interested in people breaking into computers; that's fantasy land. They want real breakins to investigate. All that computing power is there for the taking.

So Bob skips from system to system inside the growing network. There's a chart on the wall of his office; every few weeks he finds a new computer that's been caught in that giant fisherman's net. He's still his dad's good little boy, kind of: he never breaks anything and he never takes anything. He just travels, late at night when no-one's using the machines, following the route traced out by the blinking cursor, mapping the human race's brave new world. Like Dean Moriarty, he only steals cars to take joyrides. To him, the network is like a single, huge computer.

Somewhere in safekeeping he wouldn't tell me where he has the Eridani's remote control device. The Doctor handed it over to him, he said, in case the Eridani ever decide to visit Earth again. One day Bob hopes to be a sysop for NASA.

Mondy is now working somewhere in the telco. Heaven help us.

You know where Swan eventually ended up. She vanished from the rest home about a month after the Doctor and I paid our visit. The contacts I now have at the theme restaurant helped me track her down at the Bainbridge Hospital. I've been officially denied permission to visit her three times. Luis managed to escape the CIA's attentions and is being cared for by his family in Puebla. I'm told they both have lucid periods, as though waking up out of a long sleep; they can speak and write and seem quite normal, if a little slow and distant. On the anniversary of our last meeting, I ordered some flowers for both of them, over the net.

Peri had been ready to give up the ride and wade back to sh.o.r.e. But somewhere along the way, she changed her mind.