`Damn,' Wright said, `it was just on the tip of my tongue. Well, no matter. It couldn't have been that important.' He sighed. `I think,' he said, `this concludes the questions for today. I have nothing else to say.'

Graves stared at him for a moment. `You don't leave us much choice.'

Wright smiled. `I believe you call it "softening up"; is that right?'

`More or less.'

`An interesting notion,' Wright said, `but now I must leave.'

And with astonishing speed he jumped from his chair and raced for the door. The marshal crouched down and held his gun stiffly.

`Don't!' Graves shouted, and knocked the pistol away. The marshal looked stunnL d. `Don't shoot him!'

Wright was out the door. A second marshal stood outside. He wore a look of surprise as Wright slammed him in the groin with one knee. He doubled over. Wright sprinted for the stairs to the basement.

`He's going for the garage,' Graves said. He pushed the other marshal towards the door to the basement and then ran outside.

Phelps was directing a half-dozen marshals and policemen to cordon off the area.

'Wright's escaped!' Graves shouted. He ran down the street, looking for the underground garage exit.

`Where?'

`The garage.'

`Can he get out?'

The marshals and police all drew their guns. A single shot echoed inside the garage.

`How did this happen?' Phelps demanded.

Graves looked at the marshals and the cops standing by the ramp from the garage. `Don't shoot him,' he said. `Whatever happens, don't shoot him.'

There was a long silence. Nothing further was heard from inside the garage.

`I demand to know what happened,' Phelps said.

Graves listened.

Nothing.

The cops looked at each other.

`Hey,' a cop shouted, from the garage. `He went out the other exit!'

Graves instantly realized that he had made a mistake. Wright was too smart to think he could escape from the garage of this building; he would have another plan. Graves started to run. So did the police.

`Where'd he go?'

`Next building. Other block.'

Graves sprinted down the ramp into the garage and towards the other garage exit. He ran up a short flight of stairs through an open door and came out into an alley. The alley connected with the opposite block. He ran down it, the cops following, their footsteps echoing.

They saw no one.

`Where'd he go?'

Graves held up his hand. Everyone paused. They heard the sound of an engine. It was coming from the garage of a building on the adjacent block.

`Where's the exit from that garage?'

Graves ran forward. The exit must be on the street. They came out into the next street - deserted, heavily cordoned off at each end, with a police car crosswise blocking the road, cops standing around.

The sound of a racing engine. They saw a ramp.

`Don't sh -'

Wright's Alfa came up the ramp, moving very fast. The cops and marshals scrambled out of the way. They fired as they ran.

Graves felt sick.

But the Alfa was still going. It made a twisting righthand turn, slamming into a parked car. There were more gunshots. The side windows shattered into great spiderwebs, but somehow the car continued, gears grinding as it raced down the street.

Wright had planned it well, Graves thought. He would have made his escape by sneaking through the buildings if it hadn't been for the roadblock. He didn't expect that; Graves himself had ordered it on the spur of the moment.

The Alfa roared down the street.

`He wasn't expecting the roadblock,' Graves said. `He didn't count on that.'

`Whose side are you on?' Phelps demanded.

At the end of the street four policemen waited by the parked patrol car. As the Alfa bore down on them,they dropped to their knees, holding their guns stiffarmed before them.

`Don't shoot!' Graves screamed.

The cops began to fire. The tyres on the Alfa exploded. The front windshield shattered. The car wobbled, flipped on its side, and slammed into a parked car. The horn began to blare.

Graves ran over to the Alfa and tried to open the door. It was jammed shut. He looked in through the shattered windscreen and saw Wright's face, a bloody pulp, the features indistinguishable. As he watched, a tiny stream of blood spurted rhythmically from Wright's neck. Then it became a seeping red stain across his collar.

He turned away from the car.

`Is he dead?' Phelps said, running up.

`Yes,' Graves said. `He's dead.'

`How can we turn off that fucking horn?' Phelps said.

Graves stared at him and walked away.

His sense of shock was profound. Of all the alternatives, of all the possibilities and options, he had never expected this. He had never expected Wright to die.

Graves walked back up the street slowly, trying to gather his thoughts. What did he do next?

Nordmann came up to him. `That's a damned shame,' he said.

`You bet it is,' Graves said.

Nordmann looked at the crowd clustered around the wrecked car. `One thing, though,' he said.

`What's that?'

`It proves he could make a mistake.'

`It was a big one,' Graves said.

`Yes,' Nordmann said, in a calm, logical voice. `But it was a mistake.'

Graves nodded and walked back towards the surveillance building. He thought about what Nordmann had said. The more he thought about it, the more encouraged he was. Because Nordmann was right.

Wright had erred. And that was encouraging.

One of the aides came running out of the building, waving Wright's ticket. `Mr Graves,' he said. `There's something very strange going on. We just checked this ticket. He cancelled that reservation yesterday.'

Protect me from fools, Graves thought. `Of course he did.'

`Of course?'

`Look,' Graves said. `He planned to let us catch him, and he planned his escape. But he couldn't get far if we knew his real aeroplane reservation, could he?'

`Well, I guess not…'

`Keep checking the airlines. Check Los Angeles, too. You'll find he had a reservation somewhere.'

Phelps came over. `The sniffer's arrived.'

`Has it? Good.' Graves walked across the street to Wright's apartment building. Phelps trailed behind him in silence.

Finally Phelps said, `I hope you know what you're doing.'

Graves didn't answer. Because the fact was that he didn't know what he was doing. He knew only in a general way what Wright intended. Wright had made Graves a part of the total mechanism, and therefore Graves would have to cancel himself out - inactivate himself - by not doing what was expected of him.

In order to do that, he had to decipher as many elements of the total staging mechanism as possible. Only then could he determine how he was intended to participate in the staging sequence that controlled the final release of the gas.

The sniffer was the first step in deciphering the sequence.

Graves stood outside the door to Wright's apartment. Next to him Lewis held a gunlike instrument in his hand. The gun was attached to a shoulder pack with a dial. Lewis pointed the instrument at the door and ran it along the cracks and seams.

Behind them at the far end of the hallway, six people, including Phelps, stood and watched. Graves wanted everyone away from the door so that they wouldn't accidentally trip the vibration sensors. He didn't know how sensitively they were tuned, but he wasn't taking any chances.

After a moment Lewis turned away with the instrument. `Wow,' he said.

`You get a reading?'

`Yeah,' he said. `High nitrogen and oxygen content, trace phosphorus.'

`Meaning?'

`Plastic explosive, very near.'