`Christ,' Graves said.

The cop cinched the rope tight around his waist.

`Remember,' Nordmann said, `that you're counteracting the effects of the gas and you must pay out antidote in relation to your exposure to the toxin. Clear?'

`What happens if I undershoot?'

`That's worse than overshooting. It's better to give yourself too much than too little. But not too much too much.'

`When do I begin to inject?'

`Just before your exposure to the gas. If you're exposed before injecting, you'll have only five or ten seconds of clear consciousness. So do it before.'

`Four forty-five,' one of the cops said.

Graves swung one leg over the window ledge.

`You afraid of heights?' Nordmann asked.

`Terrified,' Graves said.

`Good luck,' Nordmann said as Graves crawled completely over the sill and hung there for a moment with his hands.

`We've got you,' one of the cops said.

Graves let go and began his descent down the face of the building.

He tried to balance himself against the stone wall. It was remarkable how dirty the outside of an apartment building could be. His fingers scraped over a crust of dirt and grime and pigeon droppings. He tried not to look down, but once he lost his balance and twisted upside-down, so that he was descending head first. He stared straight at the ground.

The people were minute below him. He was vaguely aware of the hot wind whistling in his ears; it was the only sound he heard. He seemed completely isolated completely alone. He reached for the stones of the apartment wall with tense fingers. He slowly pulled himself around until he was upright again.

His descent continued more slowly. He checked his watch. It was 4:47. Plenty of time, plenty of time…

He was now just above Wright's window. He could see the interior of the apartment clearly - the two tanks, yellow and black, the connecting hoses, the equipment, the snaking cables and electrical lines.

`Okay,' Nordmann shouted. `Inject yourselfl'

Graves hung dangling and twisting on the rope, nineteen floors above the street, and tried to grab his own forearm. He was clumsy; his breath came in hissing gasps; the rope was tight around his ribs: Finally he got the syringe and pushed the plunger partway down.

`Go!' Nordmann shouted.

Graves kicked away from the wall, swinging out into space, and came back with his legs stiffly extended. The glass smashed under his feet, and he was swung smoothly, almost easily, into the apartment.

He dropped to the floor, coughed, and got to his feet. Immediately the acrid piercing sting of the gas invaded his nostrils and brought tears to his eyes. He felt light-headed. The antidote isn't working, he thought, and fell to his knees. He was gasping for breath. He looked up at the equipment, the tanks above him.

He was very dizzy. He injected more antidote. And then suddenly he was all right. His mouth was dry and he was still light-headed, but he was all right. He got to his feet and moved towards the tanks. At every moment he expected to hear the ominous hiss and sizzle of the releasing gas, but it never came. He stood in the centre of the room, with the wires and cords all across the floor at his feet and the white gas drifting gently out the broken window.

He disengaged the first valve mechanism, unhooking the solenoid trip wire. Then the other mechanism. And then he sighed.

It was done.

The mechanism could not release the gas; the tanks were isolated. He relaxed, blinked his aching eyes, swallowed dryly, and checked his watch. 4:49. It hadn't even been close.

`Graves!'

That was Nordmann, shouting to him from the floor above. Graves went to the window and looked up.

`You all right?'

Graves tried to talk, but a hoarse, dry croak came out. He nodded and waved instead.

`Can't talk?'

Graves shook his head.

`That's the effect of the antidote,' Nordmann said. `You'll be okay. We want to come down. Can you open that door for us?'

Graves nodded.

`Okay. We'll come down.'

Graves opened all the other windows in the apartment, then went back to the centre of the room and crouched over the three metal boxes. One was a timer; one was a battery; the third, when he turned it over, was a hollow shell, empty inside. He stared at it and shook his head. Another diversion - but it didn't matter now.

He went to the door and looked closely at the vibration sensors. They were just rubber suction cups from a toy bow-and-arrow set, with some wires attached. Totally phoney. He sighed.

Nordmann called from the other side of the door. `Graves? You there?'

Graves let him in. He had a glimpse of two San Diego cops sprawled on the floor in the hallway as Nordmann came into the room. `Gas is dissipated now, but those poor bastards got it full. How do you feel?'

Graves nodded, smiled:

`Dry mouth?'

Graves nodded.

`You'll be all right. Just don't inject any more of that stuff. You uncouple the tanks?'

Graves pointed.

`Well,' Nordmann said. `That's it, then.' He looked around the room. `Quite an elaborate setup.'

With a pluck! Graves pulled one of the rubber suction `vibration sensors' off the wall and showed it to Nordmann.

`I'll be damned,' Nordmann said. `Phoney as a fourdollar bill. But he really kept us guessing.'

Phelps came into the room. `What's going on here?'

`The tanks have been uncoupled,' Nordmann said. `There's no danger any more.'

`Good work,' Phelps said. He said it to Nordmann. Graves was angry about that, but he made no gesture. There was no sense in giving Phelps the satisfaction.

Phelps left. Somebody brought Graves a glass of water. Graves sipped it and wandered around the room, looking at the equipment, touching it idly..

`Well, anyway,' Nordmann said. `Congratulations.'

Graves shrugged.

`You're not accepting congratulations?'

Graves finished the water, tried his voice. `I'm not sure they're in order yet.'

`Why? Surely it's clear -'

`The double whammy,' Graves said. 'Wright is a master of it.'

`That may be,' Nordmann said, `but -'

`Then where's the second punch?' Graves said. He continued to wander around the room. When he came to the scintillation counter, he clicked it on. The machine chattered loudly like an angry insect.

`Damn,' Nordmann said. `Everybody out!'

Graves laughed and shook his head. Everybody left the room quickly. Phelps was outside in the corridor, talking with policemen who were removing the two dead bodies. `What is it now?' Phelps asked.

`A second punch,' Nordmann said. `Radiation in that room.'

Phelps smiled in total triumph. `We're prepared for that,' he said. He picked up a walkie-talkie. `We have a radiation hazard on the nineteenth floor,' he said. `Get the shielding up here.'

Graves and Nordmann exchanged glances.

`Oh,' Phelps said, `I'm not a complete fool.'

`Nobody ever suggested you were a complete fool,' Nordmann said.

It took two minutes for the policeman to arrive. He entered the room with the lead cases, which were carried on small, rolling dollies. He also had a pair of long tongs. He emerged a moment later. `All clear,' he said. `Two bars of some isotope. Shielded now.'

Phelps smiled. `As soon as we heard about the explosive,' he said, `I checked truck hijackings. There were two today: one for the explosive and another for the isotope.'

`Good work,' Graves said. He said it to Nordmann.

Phelps looked pained.

Graves and Nordmann went back into the room. Nordmann said, `Satisfied now?'

`Almost.'

Nordmann laughed. `You're a hard man to satisfy.'

`It's not me,' Graves said. `It's him.'

Nordmann looked around the room. `Well,' he said, `I don't know what you expect to find here…'

`Neither do L'