A young woman looked up from the computer console. Large eyes, horn-rim glasses, dark hair. Her face was partially blocked by the ceiling pipes.

"You're not Dan," Sanders said, sounding surprised. "Where's Dan, Theresa?"

"Picking up a midterm," Theresa said. "I'm just helping run the real-time progressions. They're finishing now." I had the impression that she was older than the other students. It was hard to say why, exactly. It certainly wasn't her clothes: she wore a bright colored headband and a U2 T-shirt under a jeans jacket. But she had a calm quality that made her seem older.

"Can you switch to something else?" Sanders said, walking around the table to look at the monitor. "Because we have a rush job here. We have to help out the police." I followed Sanders, ducking pipes.

"Sure, I guess," the woman said. She started to shut down units on the desk. Her back was turned to me, and then finally I could see her. She was dark, exotic-looking, almost Eurasian. In fact she was beautiful, drop-dead beautiful. She looked like one of those high cheek-boned models in magazines. And for a moment I was confused, because this woman was too beautiful to be working in some basement electronics laboratory. It didn't make sense.

"Say hello to Theresa Asakuma," he said. "The only Japanese graduate student working here."

"Hi," I said. I blushed. I felt stupid. I felt that information was coming at me too fast. And all things considered, I would rather not have a Japanese handling these tapes. But her first name wasn't Japanese, and she didn't look Japanese, she looked Eurasian or perhaps part Japanese, so exotic, maybe she was even -

"Good morning, Lieutenant," she said. She extended her left hand, the wrong hand, for me to shake. She held it out to me sideways, the way someone does when their right hand is injured.

I shook hands with her. "Hello, Miss Asakuma."

"Theresa."

"Okay."

"Isn't she beautiful?" Sanders said, acting as if he took credit for it. "Just beautiful."

"Yes," I said. "Actually, I'm surprised you're not a model."

There was an awkward moment. I couldn't tell why. She turned quickly away.

"It never interested me," she said.

And Sanders immediately jumped in and said, "Theresa, Lieutenant Smith needs us to copy some tapes. These tapes."

Sanders held one out to her. She took it in her left hand and held it to the light. Her right hand remained bent at the elbow, pressed to her waist. Then I saw that her right arm was withered, ending in a fleshy stump protruding beyond the sleeve of her jeans jacket. It looked like the arm of a Thalidomide baby.

"Quite interesting," she said, squinting at the tape. "Eight-millimeter high density. Maybe it's the proprietary digital format we've been hearing about. The one that includes real-time image enhancement."

"I'm sorry, I don't know," I said. I was feeling foolish for having said anything about being a model. I dug into my box and brought out the playback machine.

Theresa immediately took a screwdriver and removed the top. She bent over the innards. I saw a green circuit board, a black motor, and three small crystal cylinders. "Yes. It's the new setup. Very slick. Dr. Sanders, look: they're doing it with just three heads. The board must generate component RGB, because over here - you think this is compression circuitry?"

"Probably digital to analog converter," Sanders said. "Very neat. So small." He turned to me, holding up the box. "You know how the Japanese can make things this way and we can't? They kaizen 'em. A process of deliberate, patient, continual refinements. Each year the products get a little better, a little smaller, a little cheaper. Americans don't think that way. Americans are always looking for the quantum leap, the big advance forward. Americans try to hit a home run - to knock it out of the park - and then sit back. The Japanese just hit singles all day long, and they never sit back. So with something like this, you're looking at an expression of philosophy as much as anything."

He talked like this for a while, pivoting the cylinders, admiring it. Finally I said, "Can you copy the tapes?"

"Sure," Theresa said. "From the converter, we can run a signal out of this machine and lay it down on whatever media you like. You want three-quarter? Optical master? VHS?"

"VHS," I said.

"That's easy," she said.

"But will it be an accurate copy? The people at JPL said they couldn't guarantee the copy would be accurate."

"Oh, hell, JPL," Sanders said. "They just talk like that because they work for the government. We get things done here. Right Theresa?"

But Theresa wasn't listening. I watched her plugging cables and wires, moving swiftly with her good hand, using her stump to stabilize and hold the box. Like many disabled people, her movements were so fluid it was hardly noticeable that her right hand was missing. Soon she had the small playback machine hooked to a second recorder, and several different monitors.

"What're all these?"

"To check the signal."

"You mean for playback?"

"No. The big monitor there will show the image. The others let me look at the signal characteristics, and the data map: how the image has been laid down on the tape."

I said, "You need to do that?"

"No. I just want to snoop. I'm curious about how they've set up this high-density format."

Sanders said to me, "What is the actual source material?"

"It's from an office security camera."

"And this tape is original?"

"I think so. Why?"

"Well, if it's original material we want to be extra careful with it," Sanders said. He was talking to Theresa, instructing her. "We don't want to set up any feedback loops scrambling the media surface. Or signal leaks off the heads that will compromise the integrity of the data stream."

"Don't worry," she said. "I got it handled." She pointed to her setup. "See that? It'll warn of an impedance shift. And I'm monitoring the central processor too."

"Okay," Sanders said. He was beaming like a proud parent.

"How long will this take?" I said.

"Not long. We can lay down the signal at very high speed. The rate limit is a function of the playback device, and it seems to have a fast-forward scan. So, maybe two or three minutes per tape."

I glanced at my watch. "I have a ten-thirty appointment I can't be late for, and I don't want to leave these..."

"You need all of them done?"

"Actually, just five are critical."

"Then let's do those first."

We ran the first few seconds of each tape, one after another, looking for the five that came from the cameras on the forty-sixth floor. As each tape started, I saw the camera image on the central monitor of Theresa's table. On the side monitors, signal traces bounced and jiggled like an intensive care unit. I mentioned it.

"That's just about right," she said. "Intensive care for video." She ejected one tape, stuck in another, and started it up. "Oops. Did you say this material was original? It's not. These tapes are copies."

"How do you know?"

"Because we got a windup signature." Theresa bent over the equipment, staring at the signal traces, making fine adjustments with her knobs and dials.

"I think that's what you got, yes," Sanders said. He turned to me. "You see, with video it's difficult to detect a copy in the image itself. The older analog video shows some degradation in successive generations, but in a digital system like this, there is no difference at all. Each copy is literally identical to the master."

"Then how can you say the tapes are copies?"

"Theresa isn't looking at the picture," Sanders said. "She's looking at the signal. Even though we can't detect a copy from the image, sometimes we can determine the image came from another video playback, instead of a camera."

I shook my head. "How?"

Theresa said, "It has to do with how the signal is laid down in the first half-second of taping. If the recording video is started before the playback video, there is sometimes a slight fluctuation in the signal output as the playback machine starts up. It's a mechanical function: the playback motors can't get up to speed instantaneously. There are electronic circuits in the playback machine to minimize the effect, but there's always an interval of getting up to speed."

"And that's what you detected?"

She nodded. "It's called a windup signature."

Sanders said, "And that never happens if the signal is coming direct from a camera, because a camera has no moving parts. A camera is instantaneously up to speed at all times."

I frowned. "So these tapes are copies."

"Is that bad?" Sanders said.

"I don't know. If they were copied, they might also be changed, right?"

"In theory, yes," Sanders said. "In practice, we'd have to look carefully. And it would be very hard to know for certain. These tapes come from a Japanese company?"

"Yes."

"Nakamoto?"

I nodded. "Yes."

"Frankly I'm not surprised they gave you copies," Sanders said. "The Japanese are extremely cautious. They're not very trusting of outsiders. And Japanese corporations in America feel the way we would feel doing business in Nigeria: they think they're surrounded by savages."

"Hey," Theresa said.

"Sorry," Sanders said, "but you know what I mean. The Japanese feel they have to put up with us. With our ineptitude, our slowness, our stupidity, our incompetence. That makes them self-protective. So if these tapes have any legal significance, the last thing they'd do is turn the originals over to a barbarian policeman like you. No, no, they'd give you a copy and keep the original in case they need it for their defense. Fully confident that with your inferior American video technology, you'd never be able to detect that it was a copy, anyway."

I frowned. "How long would it take to make copies?"

"Not long," Sanders said, shaking his head. "The way Theresa is scanning now, five minutes a tape. I imagine the Japanese can do it much faster. Say, two minutes a tape."

"In that case, they had plenty of time to make copies last night."

As we talked, Theresa was continuing to shuffle the tapes, looking at the first portions of each. As each image came up, she'd glance at me. I would shake my head. I was seeing all the different security cameras. Finally, the first of the tapes from the forty-sixth floor appeared, the familiar office image I had seen before.

"That's one."

"Okay. Here we go. Laying it onto VHS." Theresa started the first copy. She ran the tape forward at high speed, the images streaky and quick. On the side monitors, the signals bounced and jittered nervously.

She said, "Does this have something to do with the murder last night?"

"Yes. You know about that?"

She shrugged. "I saw it on the news. The killer died in a car crash?"

"That's right," I said.

She was turned away. The three-quarter profile of her face was strikingly beautiful, the high curve of her cheekbone. I thought of what a playboy Eddie Sakamura was known to be. I said, "Did you know him?"

"No," she said. After a moment she added, "He was Japanese."

Another moment of awkwardness descended on our little group. There was something that both Theresa and Sanders seemed to know that I did not. But I didn't know how to ask. So I watched the video.

Once again, I saw the sunlight moving across the floor. Then the room lights came up as the office personnel thinned. Now the floor was empty. And then, at high speed, Cheryl Austin appeared, followed by the man. They kissed passionately.

"Ah ha," Sanders said. "Is this it?"

"Yes."

He frowned as he watched the action progress. "You mean the murder is recorded?"

"Yes," I said. "On multiple cameras."

"You're kidding."

Sanders fell silent, watching events proceed. With the streaky high-speed image, it was difficult to see more than the basic events. The two people moving to the conference room. The sudden struggle. Forcing her back on the table. Stepping away suddenly. Leaving the room in haste.

Nobody spoke. We all watched the tape.

I glanced at Theresa. Her face was blank. The image was reflected in her glasses.

Eddie passed the mirror, and went into the dark passageway. The tape ran on for a few more seconds, and then the cassette popped out.

"That's one. You say there are multiple cameras? How many all together?"

"Five, I think," I said.

She marked the first cassette with a stick-on label. She started the second tape in the machine, and began another high-speed duplication.

I said, "These copies are exact?"

"Oh, yes."

"So they're legal?"

Sanders frowned. "Legal in what sense?"

"Well, as evidence, in a court of law - "

"Oh, no," Sanders said. "These tapes would never be admissible in a court of law."

"But if they're exact copies - "

"It's nothing to do with that. All forms of photographic evidence including video, are no longer admissible in court."

"I haven't heard that," I said.

"It hasn't happened yet," Sanders said. "The case law isn't entirely clear. But it's coming. All photographs are suspect these days. Because now, with digital systems, they can be changed perfectly. Perfectly. And that's something new. Remember years ago, how the Russians would remove politicians from photographs of their May Day line ups? It was always a crude cut-and-paste job - and you could always see that something had been done. There was a funny space between the shoulders of the remaining people. Or a discoloration on the back wall. Or you could see the brush-strokes of the retoucher who tried to smooth over the damage. But anyway, you could see it - fairly easily. You could see the picture had been altered. The whole business was laughable."