"HELL IS THIS?"Agent-in-Charge McGrath said.

He thumbed the remote and rewound the tape. Then he pressed play and watched it again. But what he saw meant nothing at all. The video screens were filled with jerky speeding images and shashy white snow.

"Hell is going on here?" he asked again.

Brogan crowded in and shook his head. Milosevic pushed closer to look. He'd brought the tape in, so he felt personally responsible for it. McGrath hit rewind again and tried once more. Same result. Just a blur of disjointed flashing pictures.

"Get the damn tech guy back in here," he shouted.

Milosevic used the phone on the credenza next to the coffeepot. Called upstairs to tech services. The head tech was in the room within a minute. The tone of Milosevic's voice had told him to hurry more effectively than any words could have.

"Damn tape won't run properly," McGrath told him.

The technician took the remote in his hand with that blend of familiarity and unfamiliarity that tech guys use the world over. They're all at home with complex equipment, but each individual piece has its own peculiarities. He peered at the buttons and pressed rewind, firmly, with a chewed thumb. The tape whirred back and he pressed play and watched the disjointed stream of flashing images and video snow.

"Can you fix that?" McGrath asked him.

The tech stopped the tape and hit rewind again. Shook his head.

"It's not broken," he said. "That's how it's supposed to be. Typical cheap surveillance video. What it does is record a freeze-frame, probably every ten seconds or so. Just one frame, every ten seconds. Like a sequence of snapshots."

"Why?" McGrath asked him.

"Cheap and easy," the guy said. "You can get a whole day on one tape that way. Low-cost, and you don't have to remember to change the cassette every three hours. You just change it in the morning. And assuming a stickup takes longer than ten seconds to complete, you've got the perp's face right there on tape, at least once."

"OK," McGrath said impatiently. "So how do we use it?"

The tech used two fingers together. Pressed play and freeze at the same time. Up on the screen came a perfect black-and-white still picture of an empty store. In the bottom left corner was Monday's date and the time, seven thirty-five in the morning. The tech held the remote out to McGrath and pointed to a small button.

"See this?" he said. "Frame-advance button. Press this and the tape rolls on to the next still. Usually for sports, right? Hockey? You can see the puck go right in the net. Or for porn. You can see whatever you need to see. But on this type of a system, it jumps you ahead ten seconds. Like on to the next snapshot, right?"

McGrath calmed down and nodded.

"Why's it in black and white?" he said.

"Cheap camera," the tech guy said. "The whole thing is a cheap system. They only put them in because the insurance companies tell them they got to."

He handed the remote to McGrath and headed back for the door.

"You want anything else, you let me know, OK?" he called.

He got no reply because everybody was staring at the screen as McGrath started inching his way through the tape. Every time he hit the frame-advance button, a broad band of white snow scrolled down the screen and unveiled a new picture, same aspect, same angle, same dim monochrome gray, but with the time code at the bottom jumped ahead ten seconds. The third frame showed a woman behind the counter. Milosevic touched the screen with his finger.

"That's the woman I spoke to," he said.

McGrath nodded.

"Wide field of view," he said. "You can see all the way from behind the counter right out into the street."

"Wide-angle lens on the camera," Brogan said. "Like a fisheye sort of thing. The owner can see everything. He can see the customers coming in and out, and he can see if the help is fiddling the register."

McGrath nodded again and trawled through Monday morning, ten seconds at a time. Customers jumped in and out of shot. The woman behind the counter jumped from side to side, fetching and carrying and ringing up the payments. Outside, cars flashed in and out of view.

"Fast-forward to twelve o'clock," Milosevic said. "This is taking way too long."

McGrath nodded and fiddled with the remote. The tape whirred forward. He pressed stop and play and freeze and came up with four o'clock in the afternoon.

"Shit," he said.

He wound back and forward a couple of times and came up with eleven forty-three and fifty seconds.

"Close as we're going to get," he said.

He kept his finger hard on the frame-advance button and the white snow scrolled continuously down the screen. One hundred and fifty-seven frames later, he stopped.

"There she is," he said.

Milosevic and Brogan shouldered together for a closer look. The still frame showed Holly Johnson on the far right of the picture. She was outside, on the sidewalk, crutch in one hand, clothes on hangers in the other. She was hauling the door open with a spare finger. The time in the bottom left of the frame was stopped at ten minutes and ten seconds past twelve noon.

"OK," McGrath said quietly. "So let's see."

He hit the button and Holly jumped halfway over to the counter. Even frozen on the misty monochrome screen, her awkward posture was plain to see. McGrath hit the button again and the snow rolled over and Holly was at the counter. Ten seconds later the Korean woman was there with her. Ten seconds after that, Holly had folded back a hem on one of her suits and was showing the woman something. Probably the position of a particular stain. The two women stayed like that for a couple of minutes, heads together for twelve frames, jumping slightly from one shot to the next. Then the Korean woman was gone and the clothes were off the counter and Holly was standing alone for five frames. Fifty seconds. Behind her on the left, a car nosed into shot on the second frame and stayed there for the next three, parked at the curb.

Then the woman was back with an armful of clean clothes in bags. She was frozen in the act of laying them flat on the counter. Ten seconds later she had torn five tags off the hangers. Ten seconds after that, she had another four lined up next to the register.

"Nine outfits," McGrath said.

"That's about right," Milosevic said. "Five for work, Monday to Friday, and I guess four for evening wear, right?"

"What about the weekend?" Brogan said. "Maybe it's five for work, two for evening wear and two at the weekend?"

"Probably wears jeans at the weekend," Milosevic said. "Jeans and a shirt. Just throws them in the machine, maybe."

"God's sake, does it matter?" McGrath said.

He pressed the button and the Korean woman's fingers were caught dancing over the register keys. The next two stills showed Holly paying in cash and accepting a couple of dollars change.

"How much is all that costing her?" Brogan asked out loud.

"Nine garments?" Milosevic said. "Best part of fifty bucks a week, that's for damn sure. I saw the price list in there. Specialized processes and gentle chemicals and all."

The next frame showed Holly starting toward the exit door on the left of the picture. The top of the Korean woman's head was visible, on her way through to the back of the store. The time was showing at twelve fifteen exactly. McGrath hitched his chair closer and stuck his face a foot from the glowing monochrome screen.

"OK," he said. "So where did you go now, Holly?"

She had the nine cleaned garments in her left hand. She was holding them up, awkwardly, so they wouldn't drag on the floor. Her right elbow was jammed into the curved metal clip of her crutch, but her hand wasn't gripping the handle. The next frame showed it reaching out to push the door open. McGrath hit the button again.

"Christ," he shouted.

Milosevic gasped out loud and Brogan looked stunned. There was no doubt about what they were seeing. The next frame showed an unknown man attacking Holly Johnson. He was tall and heavy. He was seizing her crutch with one hand and her cleaning with the other. No doubt about it. Both his arms were extended and he was taking her crutch and her cleaning away from her. He was caught in a perfect snapshot through the glass door. The three agents stared at him. There was total silence in the conference room. Then McGrath hit the button again. The time code jumped ahead ten seconds. There was another gasp as they caught their breath simultaneously.

Holly Johnson was suddenly surrounded by a triangle of three men. The tall guy who had attacked her had been joined by two more. The tall guy had Holly's cleaning slung up over his shoulder and he had seized Holly's arm. He was staring straight up into the store window like he knew a camera was in there. The other two guys were facing Holly head-on.

"They pulled guns on her," McGrath shouted. "Son of a bitch, look at that."

He thumbed the button again until the bar of snow cleared away from the bottom of the frame and the whole picture stabilized into perfect sharpness. The two new guys had their right arms bent at ninety degrees, and there was tension showing in their shoulder muscles.

"The car," Milosevic said. "They're going to put her in the car."

Beyond Holly and the triangle of men was the car which had parked up fourteen frames ago. It was just sitting there at the curb. McGrath hit the button again. The bar of white snow scrolled down. The small knot of people on the screen jumped sideways ten feet. The tall guy who had attacked Holly was leading the way into the back of the car. Holly was being pushed in after him by one of the new guys. The other new guy was opening the front passenger door. Inside the car, a fourth man was plainly visible through the side glass, sitting at the wheel.

McGrath hit the button again. The bar of snow scrolled down. The street was empty. The car was gone. Like it had never been there at all.