Look at his connect speed! He wasn't coming in over a modem. He was talking to the mainframe through one of its terminals. Swan's scalp p.r.i.c.kled. He had to be right here right here. But where? There were around forty terminals in the building.

It took her a few more minutes, a little more digging in the system, to work out which terminal he was using. She couldn't use the normal commands any sysadmin could use to find out who was where doing what: he would have noticed her in a moment, and fled. She finally grabbed the information from an error log, a single line written by the system when he'd made a typo.

The noise of the compute centre, the breathing of all those machines, was enough to mask the sound of the door swishing open. She could see the backs of three heads, three people working in the company's mainframe. She knew the number and location of every terminal in the room.

She walked right up to Bob. He was so intent on what he was doing that he simply didn't notice her. She watched over his shoulder as he patiently tried one trick after another, trying to grab root. Each time, he b.u.mped up against one of her security fixes, and crossed off his tactic from a hand-written list.

Swan caught her bottom lip between her teeth. There was one she'd missed he was in her account! Without a pause, he listed her files, spotted the new and huge program created by the monster, and set up an ftp session to transfer a copy of it somewhere else. She had to restrain herself from grabbing his shoulders and flinging him away from the terminal, spinning in his chair. She had to see where that file was being sent to.

He only looked up when the security guard she'd called clumped into the room, his billy club banging against the doors as they slid open. Bob froze when he saw her, his mouth locked open in shock, his hands curled over the keyboard like claws.

80.

Robert Salmon Snr was not impressed.

He drove from the centre of Washington to meet us in a parking lot in Crystal City, close to TLA. The Doctor, looking serious in his dark suit, shook hands with Salmon Senior. 'It's good to meet you face to face at last. I only wish the circ.u.mstances were better.'

Bob's father was a scowl above a moustache, keeping his temper under control while he dealt with the crisis in good military fashion. When the Doctor introduced Peri and I, he dismissed us with a glance. 'Maybe you can explain why my boy is in trouble with the police. He was mighty vague about it.'

'Mr Salmon,' said the Doctor, 'Bob has been helping me to investigate a serious threat to your nation's security.' He was choosing his words carefully 'He rose to a similar challenge as a very young man.'

'Yes, he did. But everything we did five years ago was authorised. There was never any reason for the police to be phoning me about my son.'

'I can't say too much,' said the Doctor, 'but the stakes are much higher this time.' Mr Salmon's eyebrows lifted; last time the stakes had been nuclear blackmail.

'You can say a whole lot more, Doctor. You can explain why it's necessary to involve a vulnerable young man in your mission. You can explain just what threat makes that a responsible thing to do.'

The Doctor said, 'For one thing, Mr Salmon, your son is an adult capable of making his own choices. And for another '

Peri said, 'Shouldn't we go and get Bob out of jail?'

The Doctor and Mr Salmon both glanced at her. Peri's voice dropped, but she stood her ground. 'He is waiting for us.'

'You're right, of course,' said the Doctor. 'Mr Salmon, I'm quite prepared to pay for Bob's release from custody.'

Robert Senior wanted to say 'Don't be ridiculous; but instead he said, 'That won't be necessary.'

And so young Bob was extracted from the clutches of the law, having spent an educational night in the tank, and driven back to his parents' house in the 'burbs. Father and son didn't say a word to one another in the car, but Bob asked,'Is Mom here?'

as Salmon Snr rattled the keys in the lock.

'No. I didn't call het' Bob sagged with relief into a kitchen chair, but his father said, 'It's up to you to tell her yourself.'

'Oh.'

Mr Salmon pulled out a chair, then stood for a few long moments, his hand on the back of it, stroking the wood.

Finally he sat down.

'As soon as you moved out of this house,' he began, 'your life was your own. If you want to skip work and run around the countryside chasing UFOs, it's none of our business.' Bob knew better than to interrupt. 'But as soon as your mother and I become involved, it's our business too.'

Pause. 'Dad,' said Bob, 'I have never bulls.h.i.tted you in my life. Have I?' Mr Salmon's mouth flattened beneath his moustache in a look of irritation. Bob rushed on, 'You know I would never do anything like that without a meaningful reason. I wish you could have been with us when we visited Ritchie.'

'Who's this Richie?'

'It's a place,' said Bob. 'A little town. A piece of technology got loose there and it's done a lot of damage.

We're trying to stop it doing any more damage.'

'When you broke into that building,' said his father, 'did you understand what you were putting on the line?'

'I didn't break in. I just walked in. All she's got on me is trespa.s.sing.'

'That could be a lot if you're trying to convince a computer company to hire you,' said his father.

'I know. Swan has got me by the prairie oysters. She can make a lot out of that little charge. I knew when I went in there that she could wreck my career or my chances of college.

A couple of days ago I wouldn't have dared to get anywhere near her. But she's got something that's at least as dangerous as what Professor Xerxes tried to put in your program when I was fifteen.

'Convince me,' said Robert Senior.

'Xerxes was only aiming to corrupt one program. Imagine if he had been able to install a trapdoor in every every machine. The military, the colleges and it doesn't matter which box they have or what system they're running on it. Swan has something that can break into all of them. And once that thing gets loose on ARPAnet, it'll be like the tapeworm in machine. The military, the colleges and it doesn't matter which box they have or what system they're running on it. Swan has something that can break into all of them. And once that thing gets loose on ARPAnet, it'll be like the tapeworm in Shockwave Rider Shockwave Rider. There'll be no way to stop it or stamp it out except to kill the net itself.'

'What about vaccinating the computers before that can happen?'

'To do that, we need to a.n.a.lyse what Swan's got. That's why I went in there.'

'All right,' said his father. 'But Xerxes' trapdoor would only have affected computers running the new software.

Sounds like Swan's program, or whatever it is, will only affect computers on the ARPAnet. That's only a couple hundred machines.'

'But it's growing all the time,' said Bob. 'In the future, there could be hundreds more, even thousands of them connected through the network. Imagine if someone was prepared to wait twenty or forty years to take over all the military and science computers. They'd have a backdoor into every computer on the net all that tactical and research information. Or they could simply cripple the net. Kill all those projects, and the military's alternative communications capability.'

Bob's father nodded slowly, digesting that. 'If we can prove what Swan is doing, the charge against you will look like a well-meaning mistake instead of a crime. I may be able to pull some strings to get a search warrant. But I'd need some solid evidence. Have you got that?'

Bob shook his head. 'Nothing that would convince the police. I mean, that's what I was there to get.'

'Then what can I do to help?'

Bob said, 'Let me keep helping the Doctor. He needs a programmer he knows he can rely on.'

Mr Salmon took a good, long look at his son. 'I don't want to have to bail you out again,' he said.

Bob gave him a shy grin. 'I don't want to have to be bailed out again.'

'Do we have an agreement?'

They shook hands. Bob's dad went to the freezer to fish out some frozen Chinese food for the pair of them.

'I'm glad I don't have to deal with that on a regular basis,'

said the Doctor.

Peri agreed. 'My parents would've strangled you ages ago.'

The Doctor had been unusually quiet on the journey back to my apartment. Letting Bob take risks was one thing, but having to deal with an angry dad was quite another. I wondered if the Doctor just didn't think of the danger, or if he hosted his sidekicks with their missions enough to let them face it. More likely, I thought, the magnitude of the problem wiped any thought of personal consequences from his field of view.

There was an email for the Doctor waiting in Bob's university account. It was Swan, making her gambit: Trespa.s.sing can easily lead to industrial espionage. I'll forgive your trespa.s.ses if you'll hand over the instruction manual (or point me to it).

The Doctor barked with laughter. 'She doesn't know what to do with it! She's asking us!'

Peri was chewing on the lid of her highlighter pen. 'Hey,'

she said. 'Why does she think you would have the manual?

Doesn't she know it's from another planet?'

'She must a.s.sume it's a product of military research,'

mused the Doctor. 'In which case, she's probably searching the ARPAnet for information about it.'

I said, 'She must know they wouldn't leave cla.s.sified info lying around on ARPAnet where anyone could get at it'

'Hence her demand that we tell her where to look,' said the Doctor. 'But she would also know that if she searches long and hard enough on the uncla.s.sified systems, she might put together enough clues to tell her where to look off the net. I doubt even a cla.s.sified military computer would be a great challenge for Swan.'

'Then why ask us at all?' said Peri.

'It would be far more efficient if we just coughed up the info,' I said.

'The crucial thing is that she doesn't know what she has or what she can do with it. Not yet. The Savant hasn't told her.

Which is interesting in itself... ah.'

A new email had arrived in Bob's account. The Doctor opened it up: it was from Swan, but this time, it was just a list of Internet addresses. Each of the curt acronyms represented one machine, one node on the net.

'What's she trying to tell us now?' said Peri.

The Doctor looked like the cream-swiping cat. 'Bob's mission was a success after all,' he purred. 'This is a copy of a file which Swan saved in coded form a few minutes ago.

Before she caught him, Bob installed a program on her system which quietly sends us a readable copy of any file she encrypts.'

'So we get to read anything she doesn't want us to read?'

said Peri.

'Exactly.'

'We're gonna need more diskettes,' said Peri.

The Doctor was saying, 'In this case, I a.s.sume we're looking at a list of the Internet sites she's already searched. He ran his finger down the screen. 'Which would mean...' he began to hammer at the keyboard in earnest.

We watched as he spent a few moments breaking into a poorly guarded college computer. 'Not here,' he said. 'Then...'

He used the telnet command to leap from that machine to another. This one had no protection at all; he simply logged into a maintenance account with root privileges. He stabbed a finger at the screen. 'There,' he said. One of the users listed on the system was our friend fionnuala. She hadn't even bothered to disguise her presence.

The Doctor sent her a text message: 'You won't find a manual because there is no manual.'

I could imagine Swan's response surprise, followed by hindbrain rage. Whatever she was feeling, she let none of it show on the screen. 'Hand it over or you know who will suffer the consequences.'

The Doctor responded by sending a message to the sysop, warning him of intruders on his system. The sysadmin took the message seriously: a few minutes later, while Swan was in the middle of searching through the system's files, both she and the Doctor were kicked off.

The Doctor glanced at Swan's list of computers again, and compared it to Bob's map of the net. 'Logically, he said,'her next destination should be... here.'

He jumped to the next computer, took a moment to break in, and started searching for signs of Swan's presence. 'She's set up an orderly search pattern,' he muttered to himself. 'I doubt she has the imagination to break out of it now. There.'

This time Swan had hidden herself from the list of users currently logged on, but the Doctor found her through the tell-tale signs of her activity. 'None knows how to use that thing safely,' he told her, again in a text message. 'Least of all myself.'

Swan shot back 'GO AWAY!!!' It was the first time we'd seen her be anything but reptile cold. The Doctor was starting to get under her skin.

She jumped again. The Doctor followed her again. It took him two tries ten minutes to find the system she was on.

She was in the list of users again, working carelessly and fast, rummaging through the files for anything that might give her a clue as to what she could do with the Savant.

It went on that way for an hour. The Doctor would lecture Swan, Swan would leap away to another computer somewhere on the net, the Doctor would find her again. Her text responses became more abusive, then stopped all together. She simply could not believe that he could find her again and again, following her through the maze like Theseus guided by his string.

I couldn't help thinking of the time I'd watched Stray Cat playing with a mouse she caught out on the balcony. Instead of just killing it, she kept patting it, or pretending to ignore it all to see if it had any energy left. Even a mouse can give a cat a potentially fatal bite if it isn't exhausted before the cat goes in for the kill I saw it go for her face more than once. Stray Cat kept her head well back, and used her paw to tap it and tap it again, wearing it down until it couldn't fight back any more.