'We could up the ante,' someone suggested. 'Put up another nuke at a greater distance, but still in kill range. If the hunter-killers take out the first, we take out everything left with the second nuke. And we lay down an ultimatum. Use one or both nukes if any hunter-killers approach the second.'

Isaacs made a couple of personal notes to augment the record of the session which would be transcribed and stored in computer memory. 'The President may not want to escalate in that direction,' he replied. 'Let's see what else we can come up with.'

'What's to keep the Russians from putting up their own nuke?'

'They may be trying to keep some lid on this in their own way,' answered Isaacs. 'But that's clearly one of their options. Let's come back to that and see if we can map out what would drive them to it.'

'How fast are those hunter-killers?' a new voice asked.

'Can the nuke be scooted somewhere else before they can respond? For instance out of their range, but still within nuclear range?'

Another voice answered. 'Tough to outrun an explosion.'

'Yeah, true,' the first voice answered thoughtfully, 'but at least you would be putting the pressure on them to make the first overt move.'

'Maybe,' came the second voice, 'but if you force them to blast the nuke, they may figure they're already committed and start using the laser on everything else in orbit.'

Isaacs had the projector turned off and the lights back on. Around the room, people sat erect from the postures they had assumed to peer at the slide.

'Let's talk some more about the options of the Soviets,' Isaacs requested. 'What are they apt to do?'

'Well,' said Earls, 'they could fire a charge over our bow, so to speak, if the charges are shaped and the explosion can be directed, just a little sabre rattling without changing the status quo. Or they could go for broke, zap us with a hunter-killer then use the laser with impunity. Or they could just fire the laser, betting that we won't use the nuke even if the laser is actually used. Hunter-killers don't do them much good then, but there is some chance any explosion would trigger the nuke, and they may not want to risk that.

'Come to think of it,' Baris wagged a finger, 'maybe they would want to try exactly that, just go ahead and use the hunter-killers. If the nuke goes, they have us for using atomics in space. If we chicken out, they have free use of the laser and our vaunted nuclear threat comes to nothing. Just the kind of pitiful giant posture they like to trap us in.'

Baris scratched his head as he thought. 'If that's their most obvious move, then we just force them to it if we try to move the nuke out of range of the hunter-killers. That seems to me to be the question. Will they risk our wrath and perhaps a nuclear explosion by using the hunter-killers, or just sit tight? Do we use the nuke without direct provocation, or try to horse it out to a greater distance? Or do we just sit with them and sweat blood?' He stopped and looked around the room for a reply.

The discussion continued for an hour and a half. They continued to produce ideas, filtering out the unproductive ones, refining and developing the good ones. A priority list of intelligence targets was constructed and assignments banded out. Isaacs finally called a halt so that all could turn to their individual tasks.

The next day, Monday, Isaacs finally found some time to pursue his personal agenda. He'd promised Danielson more data to refine her predictions of the upcoming event in Nagasaki. Now he looked across the desk at the young Navy lieutenant. Philip Szkada had been placed in nominal charge of the Navy's surveillance of the strange sonar signal. Although the day was officially a part of the three-day holiday weekend, he had agreed to meet Isaacs in Rutherford 's old office.

'It's a pleasure to see you again, Mr Isaacs,' said Szkada.

'I guess the last time was when you came to visit Captain Rutherford just before — just before -' His face took on a heavy pinched look. 'It's still difficult to believe he's gone.

By all rights I should have made that trip, but he insisted on going himself.'

He was silent for a moment, then met Isaacs's gaze.

'What can I do for you today?'

'You know that Avery Rutherford was a good friend of mine. I'm interested in his death for both personal and professional reasons. When we spoke over the phone at the time, you indicated uncertainty as to whether the ship's sinking was related to its surveillance mission, but that the surveillance programme was downgraded afterwards. I was hoping to learn more about the circumstances and the mission.'

'There's not much to say. In fact, under the shock of the moment, I may have said too much. From reports of the survivors and some scattered physical evidence, it appears that the ship's turbine exploded. There's no firm reason to conclude that the fate of the ship was related to her mission.'

He paused and made a tent of his fingers. He cleared his throat before continuing.

'The mission itself is a confidential Navy investigation. With all respect, sir, I'm not sure you have a need to know.'

Isaacs expected and admired that response. He would have demanded it of his own subordinates. He could not accept it, however. He turned the tack back to the personal issue.

'You said you should have been on the ship. Avery wasn't the sort to pull rank unnecessarily.'

'No, sir, he wasn't. But in this case I had worked out the ideas that were the basis of the mission. I expected to go.'

'Avery had nothing to do with the planning? Strange then that he would have involved himself in that way.'

'Well, of course, we discussed the mission. Some information had been kicking around and I managed to make sense of it.'

'Avery had no role in that?'

'Not really. Some things just fell into place for me after one of our discussions.'

Szkada paused and looked thoughtful.

'He did ask me some leading questions. With the pleasure of seeing it fit together, I didn't give much thought to the actual process that brought me to the conclusion.'

He looked up towards the far wall over Isaacs's right shoulder. Isaacs remained silent, reading the workings of his face. He saw the frown lines disappear, to be replaced by arched eyebrows and a look of mild surprise. After a moment another idea hit him and he leaned forward and locked eyes with Isaacs.

'He fed me the idea, didn't he?'

He pointed an index finger at Isaacs.

'And you gave it to him!'

Isaacs admired this perspicacity, even somewhat belated. No wonder Rutherford had spoken highly of him.

'Lieutenant, I sent my best friend to his death. I want to know what killed him.'

'Mr Isaacs, I really can't help you. I presume you already know what the mission was.'

Isaacs wanted to make it easy for him.

'You're monitoring a sonar signal that moves on a trajectory which is fixed with respect to the stars.'

Even having deduced Isaacs was aware of the mission, the frank statement startled Szkada. Isaacs continued.

'We have some seismic data showing the same behaviour. In case you're curious,' he smiled, 'the idea of the fixed trajectory actually came from one of my people, a counterpart of yours in the Agency.'

'You must know all I do then,' Szkada commented. 'I don't have the authority to push for a full investigation here, so we're just in a monitoring mode. We've learned nothing new. Perhaps we could collaborate?' Szkada suggested, 'with an official request from the Agency.' Isaacs cut him off with a raised hand.

'Lieutenant, we have a similar problem. Our mission has been officially shelved, partly because my superior knows that your superiors are nominally continuing the investigation. I want to say that I am here unofficially today.