`I know how you feel,' Phelps said.

`Do you?' Graves asked.

`Yes. You're… ambivalent about the section.'

`I'm ambivalent about the domestic activities.'

`We all are,' Phelps said. He said it easily, in the smooth, oil-on-the-waters manner that he had perfected. And his father before him. Phelps' father had been an under-secretary of state during the Roosevelt administration. Phelps himself was a product of the Dalton School, Andover, Yale, and Harvard Law School. If he sat still, ivy would sprout from his ears. But he never sat still.

`How do you find San Diego?' he asked, walking along with his maddeningly springy step.

`Boring and hot.'

Phelps sighed. `Don't blame me. I didn't choose it.'

Graves did not reply. They continued down a corridor and came upon a guard, who nodded to Phelps. `Good morning, Mr Phelps.' And to Graves: `Good morning, sir.' Phelps flashed his pink card; so did Graves. The guard allowed them to pass farther down the corridor past a large banner that read FIRST CWS SERVICE ON COACH.

`You've got a guard already,' Graves said.

`There's a lot of expensive equipment to look after,' Phelps said. They made a right turn and entered a conference room.

There were just four of them: Graves; Phelps, looking springy and alert as he greeted everyone; Decker, who was thin and dark, intense-looking; and Venn, who was nearly fifty, greying, sloppy in his dress. Graves had never met Decker or Venn before, but he knew they were both scientists. They were too academic and too uncomfortable to be anything else.

Phelps ran the meeting. `This is John Graves, who is the world's foremost expert on John Wright.' He smiled slightly. `Mr Graves has plenty of background, so you can speak as technically as you want. Decker, why don't you begin.'

Decker cleared his throat and opened a briefcase in front of him, removing a sheaf of computer printout. He slipped through the green pages as he spoke. `I've been working in Special Projects Division for the last six months,' he said. `I was assigned to establish redundancy programmes on certain limited-access files so that we could check call-up locations to these data banks, which are mostly located in Arlington Hall in Washington.'

He paused and glanced at Graves to see if the information was making sense. Graves nodded.

`The problem is basically one of access-line proliferation. A data bank is just a collection of information stored on magnetic tape drums. It can be anywhere in the country. To get information out of it, you need to hook into the main computer with an access substation. That can also be anywhere in the country. Every major data bank has a large number of access substations. For limited or special-purpose access - stations that need to draw out information once or twice a week, let's say - we employ commercial telephone lines; we don't have our own lines. To tie in to a peripheral computer substation, you telephone a call number and hook your phone up to the computer terminal. That's it. As long as you have a half-duplex or full-duplex telephone line, you're in business.'

Graves nodded. `How is the call number coded?'

`We'll come to that,' Decker said, looking at Venn. `For now, we'll concentrate on the system. Some of the major data banks, like the ones held by Defence, may have five hundred or a thousand access lines. A year ago, Wilkens' congressional committee started to worry about unauthorized tapping into those access lines. In theory, a bright boy who knew computers could tap into the system and call out any information he wanted from the data banks. He could get all sorts of classified information.'

Decker sighed. `So I was hired to install redundancy checks on the system. Echo checks, bit additions, that sort of thing. My job was to make sure we could verify which stations drew out information from the data banks, and what information they drew. I finished that work a month ago.'

Graves glanced at Phelps. Phelps was watching them all intently, pretending he was following the discussion. Graves knew that it was over Phelps' head.

`Just before I finished,' Decker said, `we discovered that an unauthorized station was tapping into the system. We called it Sigma Station, but we were unable to characterize it. By that I mean that we knew Sigma was drawing information, but we didn't know where, or how.'

He flipped to a green sheet of computer printout and pushed it across the table to Graves. `Sigma is the underlined station. You can see that on this particular day, July 21st, 1972, it tapped into the system at ten oh four rnt Eastern time and maintained the contact for seven minutes; then it broke out. We determined that Sigma was tapping in at around ten o'clock two or three nights a week. But that was all we knew.'

Decker turned to Venn, who said, `I came into the picture at this point. I'd been at Bell Labs working on telephone tracer mechanisms. The telephone company has a problem with unauthorized calls - calls verbally charged to a phone number, calls charged to a wrong credit card number, that kind of thing. I was working on a computer tracing system. Defence asked me to look at the Sigma Station problem.'

`One ought to say,' Phelps said, `that the data bank being tapped by Sigma was a Defence bank.'

`Yes,' Venn said. `It was a Defence bank. With two or three taps a week at about ten PM. That was all I knew when I began. However, I made some simple assumptions. First, you've got to have a computer terminal in order to tap the system. That is, once you've called the number that links you to the computer, you must use a teletypewriting or CRT apparatus compatible with the Defence system.'

`Are those terminals common?'

`No,' Venn said. `They are quite advanced and fairly uncommon. I started with a list of them.'

Graves nodded.

`Then I considered the timing. Ten PM Eastern time is seven rht in California, where most of these sophisticated terminals in defence industry applications are located. If an employee were illegally using a terminal to tap into Defence, he couldn't do it during office hours. On the other hand, it requires an extraordinary access to get into an East Coast terminal location at ten at night - or into a Midwest location at eight or nine. Therefore Sigma was probably on the West Coast.'

`So you checked the West Coast terminals?'

`Yes. Because in order to hook into the Defence system, you'd have to unhook from your existing system. What corporation, R amp;D group, or production unit had a terminal that was unhooked at seven Pm Western time twice a week? Answer: None. New question: What group had its terminals repaired twice a week? Repairing would entail unhooking. Answer: The Southern California Association of Insurance Underwriters, a company based in San Diego.'

Graves said, `So you investigated the repairman and you found -'

`We found our man,' Venn said, looking slightly annoyed with Graves. `His name is Timothy Drew. He has been doing repair work on the SC Association computers for about six weeks. It turns out nobody authorized those repairs; he just showed up and -'

`But you haven't picked him up.'

Phelps coughed. `No, actually. We haven't picked him up yet because he's -'

`Disappeared,' Graves said.

`That's right,' Phelps said. `How did you know?'

`Tim Drew is a friend of John Wright. He's had dinner with him several times a week for the last month or so.' As he spoke, Graves had a mental image of Drew - early thirties, blond-looking, muscular. Graves had run a check on him some weeks back and had discovered only that Drew was an ex-Army lieutenant, discharged one year before. A clean record in computer work, nothing good, nothing bad.

`We weren't able to find him,' Venn said, `but we're still looking. We thought -'

Graves said, `There's only one thing I want to know. What information did Drew tap from the classified files?'