`Near the door?'

`Probably just on the other side,' he said.

Graves said, `Is there any chance you're wrong?'

`The sniffer is never wrong,' he said. `You've got oxide of nitrogen fumes, and that's explosives. You can count on it.'

`All right,' Graves said. He walked away from the door. He had to trust the sniffer. It had been developed for use in Vietnam and had been adapted for customs operations, smuggling, and so on. It was incredibly sensitive and incredibly accurate. If the sniffer said plastic explosive was behind the door, he had to believe it. He walked back to Phelps at the end of the hallway.

`Well?'

`There's explosive on the other side of the door.'

`Nice,' Phelps said. `What do we do now?'

`Try to get a better look inside the apartment,' Graves said. He glanced at his watch.

`It's four ten,' Phelps said. `When did your friend say it would go off?'

`Five,' Graves said.

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

Graves sighed. He wondered if he could ever explain to Phelps that that wasn't the problem. The problem was figuring out what Wright expected him to do - and then not doing it.

Across the street in the surveillance room looking down on Wright's apartment, he talked to Nordmann. Nordmann had brought a cardboard box full of medical supplies - syringes, needles, bottles of liquid. He was frowning down at it. `This is the best I could manage on short notice,' he said.

`Will it work?' Graves said.

`It's the standard therapy,' Nordmann said. `But we haven't got much. This quantity will treat two or three people for exposure, that's all.'

`Then let's make sure it doesn't come to that.'

Nordmann smiled slightly. `It better not,' he said. `Because you need somebody alive and well to administer it.'

`Is it hard to administer?'

`Tricky,' Nordmann said. `There are two different chemicals, atropine and parladoxime. They have to be balanced.'

Graves sighed. `So the antidote is a binary, too.'

`In a sense. The two chemicals treat different effects of the gas. One treats the peripheral nervous system, the other the central. The chemicals are dangerous in themselves, which makes it all much harder.'

`Fighting fire with fire?'

`In a sense,' Nordmann said.

The two men stood staring out the window at the apartment opposite. Phelps was in a corner using a walkie-talkie. `You in position?'

A response crackled back. `In position, sir.'

`Very good.' Phelps clicked off the walkie-talkie. `We've got two cops stationed outside the door to that apartment,' he said.

`Fine,' Graves said. `Just so they don't get too close to the door.'

`I have them ten feet away.'

`That should be fine.'

In the hallway outside Wright's apartment, officers Martin and Jencks of the San Diego Police Department stared at the closed door and leaned against the wall.

`You understand any of this?' Jencks said.

`Nope,' Martin said.

`But they said not to get too close to the door.'

'That's right.'

`You know why?'

`I don't know nothing,' Martin said. He took out a cigarette. `You got a match?'

`Maybe we shouldn't smoke…'

`Who's going to know?' Martin said.

Jencks gave him a match.

Graves stood with Nordmann in the surveillance room across the street.

'Wright booby-trapped the apartment?'

`Elaborately,' Graves said. `He told me some of it. I'm sure he didn't tell me everything.'

`And it goes off at five?'

`Yes.'

`Forty-five minutes from now,' Nordmann said. `Is the Navy sending people with protective suits? Because protected people could just walk right in.'

`Nobody can walk right in,' Graves said. `He's wired the room with explosive. That's why we've got the guards over there.'

Nordmann grimaced. `Explosive?'

`Twenty pounds of it.'

The TV in the corner of the room showed the Convention. A monotonous voice was saying, `Mr Chairman… Mr Chairman, we request the floor… Mr Chairman…' There was the loud banging of a gavel.

`Turn that damned thing off,' Graves said. Someone turned it off.

At the window two men grunted as they lifted a huge lens onto a heavy-duty tripod. It was screwed into place and adjusted. `Ready, Mr Graves.'

`Thank you.' Graves went to the window.

`What's that?' Nordmann said.

`A fifteen-hundred-millimeter telephoto,' Graves said. `It's the best look we can get.'

He peered through the giant lens. The view was so enormously magnified that at first he didn't know what he was looking at. Using a fine-knurled knob, he moved the lens and saw he was focused on a crack in the floor. He moved across the floor to the boxes. He shifted the lens upward, examining each box in detail.

`Take a look at this,' he said, stepping away.

Nordmann squinted through the lens. `Three stacked boxes,' he said. `I can't make out much…'

`Neither can L' Graves folded his arms across his chest and stared out the window. He tried to think logically, but he was having trouble; Wright's death had unnerved him, whether he wanted to admit it or not.

And the system seemed so complicated. Staging sequences, timers, vibration sensors, explosives… His head ached. How the hell would he unravel it?

`Let's work it backward,' Nordmann said. `What's the most important element in the system?'

`The gas.'

`How is it controlled?'

`There are spring-loaded valve mechanisms. They can be tripped by a solenoid.'

`And they presumably have a timer of some kind.'

`Presumably.'

`Battery-powered or line-powered?'

`Well, he's plugged one of the boxes into the wall. But the valve mechanisms are probably batterypowered.'

Nordmann nodded. `That makes sense,' he said. `He wouldn't have the most important elements dependent on an external system. So what did he plug into the wall?'

`I don't know.'

`Vibration sensors?'

`Maybe,' Graves said. He looked at his watch. It was 4:20. He would have to move soon. What had Wright expected him to do? The psychological report was folded up in his pocket. He took it out and looked at the last few lines.

IF THERE ARE ANY DEFECTS OR HIDDEN FLAWS IN HIS BEHAVIOUR, THEY ARE HIS IMPULSIVENESS AND HIS DESIRE TO FINISH A TEST SITUATION RAPIDLY.

Well, he didn't have much choice now. He was going to have to make a move, and soon.

`You know,' Nordmann said thoughtfully, `most of the equipment in that room is defensive. It's designed to keep people out of there until the gas is ready to be released. But I suspect some of those defences. are meant to be penetrated.'

`I agree,' Graves said. `And in any case, we have to start penetrating.'

`Wall current first?' Nordmann asked.

Graves nodded. He glanced at Phelps, who was sitting in a corner of the room literally chewing his nails. Graves sent Lewis across the street to disconnect power to the apartment. Four minutes later, the power was off. Graves watched through the big telephoto lens. He saw a single yellow pilot light in the vibration sensor box go out.

`Well,' Nordmann said, `that's a start. We've killed part of the system.'

`Have we?' Graves said. He watched through the telephoto as the solenoid mechanism tripped open the tank valves, then a moment later tripped them shut.

The apartment became filled with whitish gas.

`What's happening?' Phelps said, very agitated.

`Quick,' Graves said. `Those cops. Tell the cops.'

`What cops?' Phelps said.

Officer Martin finished his cigarette and ground it out on the floor. His heel squeaked.

`Sssh,' Jencks said, suddenly tense.

`What is it?'

`Sssssh. Listen.'

The two men listened in silence. There was a hissing. `You hear that?' Jencks said.

`Yeah. It's coming from the room.'

`Are you sure?'