"That's what I gathered." He nodded. "What was it you said the other day? Something about efficiency?"

"I said they only seem interested in the most logical, efficient way to kill us," she said. "Oh! I see what you're getting at, and you're right. Their sole criteria for evaluating methods seems to be pragmatism, not the 'cruelty' or 'compassion' they entail."

"Exactly. But it's not that way for a Troll."

"No." Her voice was even, but he felt a distant snarl under its calm. "If there are two equally efficient means to an end, they invariably choose what we'd call the crueler one. They've even been known to accept a certain amount of inefficiency if it lets them indulge themselves."

"All right." He drew on his pipe and blew an almost perfect smoke ring. The wind snatched it away, shredding it eagerly. There seemed to be some obscure metaphor to that, he reflected uneasily, but he kept the thought out of his tone as he continued. "Let's look at another point. We know he's dangerous, but just how dangerous is he?" She looked up, an arrested light in her eyes. "What I'm getting at is that he may not be in a position to start right out doing whatever he's planning on."

"You know," she said slowly, "you may have a point. He's on his own. I know that intellectually, but I haven't been thinking about his problems, only mine."

"I know." He drew on his pipe again. "Generally speaking, that's the smart way to think. Figure the worst-case scenario, then do what you can to stop it. But in this case, especially, you have to run a threat analysis based on his limitations, as well." He cocked an eyebrow at her, and she nodded. "All right, as I see it, he's got both problems and advantages.

"First, his problems. He's alone, without any support base. He's outnumbered by billions of primitives who've already proved they can kill him, at least under optimal conditions. You're pretty sure he doesn't have any bio weapons, and if he has any nukes left, they're only tactical weapons-by his standards, anyway-in the kiloton range; not really big enough for genocidal purposes. Finally, he probably doesn't understand normal human psychology a lot better than we understand his.

"Next, his advantages. He's got a five-century technical lead and the initiative. He's the only one who knows exactly what he intends to do. His enemies-the present-day human race-are split into mutually suspicious national groupings. We don't know where he is. He can read about a third of all human minds he encounters. And, finally, he can influence the minds he can contact."

"There are a couple of other points," she said thoughtfully. "For one thing, he can't possibly mingle openly with his targets, so whatever he does, he's going to have to do it from concealment. On the other hand, he's well-armed. His organic component's basically a plug-in unit, and he's undoubtedly got a combat chassis in his fighter, not to mention a small number of combat mechs."

"Just how tough is he in those terms?" Aston asked.

"Pretty damned tough," she replied frankly. "I've been trying to remember all I can about your period's weapons. Your nukes can take him out, and some of your heavy weapons might be able to, but I doubt any of your man-portable ones can do it. Until I've had a chance to examine some of your armored vehicles firsthand, I can't give you much of a relative meterstick, and even that depends on what type of combat chassis he has." She nibbled the tip of one finger thoughtfully.

"At the least, he'll mount some light energy weapons, some close-in 'sweeper' projectile weapons, and some battle screen to cover it. Then, too, his brain's organic; that gives him both advantages and disadvantages over a computer. He's creative and intuitive, but his ability to handle simultaneous actions is limited-he can be distracted by overloading his sensors in a tactical confrontation. On the other hand, his weapons are part of him. He doesn't have to draw one, and his electronic systems take care of little things like aiming and firing once his brain decides to do it. Remember that, Dick; one thing Trolls don't do is miss."

"Okay, so he's tough but not exactly unstoppable."

"That's a fair enough summation," she agreed. "His combat mechs aren't as tough as he is, either, and their autonomous systems are inferior to human capabilities. He can handle them direct, but, again, he can't begin to multi-task as well as a true AI, so the more he tries to run at once, the less effectively he can handle any one of them."

"All right," Aston said. "On that basis, does he really have the capability-by himself and out of his present resources-to wipe us out?"

"No," she said positively, and drew a deep breath. A vast tension-even more terrible for the fact that she had given so little sign of feeling it-washed out of her. "He could do a lot of damage, but not that much."

"Fine. Now, is he likely to risk revealing himself or exposing himself to our weapon systems until he figures he can wipe us out?"

"No," she said again.

"Does he know enough about our world to figure out where and how to get his hands on what he'd need to wipe us out?"

"No way." She shook her head emphatically. "He's going to have to spend quite a while educating himself."

"All right. So we've probably got at least a little time before he can act, which leads to my final question. It may sound a bit outrageous, but what's the cruelest thing a Troll could do to the human race?"

"Destroy it," she said promptly, then paused, an arrested light in her eyes. "Wait a tick," she said softly. "Wait... ." Her voice trailed off and her brows knitted. Then her face smoothed. "Do you know, I never even considered that angle," she said quietly.

"I know. I've been listening to you, and I think you've been fighting each other so long it's hard for you to think about a Troll in any terms other than mutual and absolute destruction. But given the fact that he can't exterminate us immediately and that he hates the Kangas as much as he does us, is it possible he might reject their objectives and settle for something else?" He looked down into her eyes, and understanding looked back. "Remember, his kind's been enslaved from the day they were first created. Isn't it possible that he might decide it was more fitting to enslave us rather than destroy us?"

"Yes," she said very, very softly. "Oh, yes-and especially if he thinks he can use us to wipe the Kangas when they finally do turn up."

"I know we can't afford to assume that that's exactly what he'll try to do, but we've got to assume it may be."

"Agreed." She was back on balance, probing at the new possibilities. "In either case, we've got more time than I was afraid we did, but I think you've put your finger on it. From his viewpoint, enslaving the human race would be far more fitting than destroying it. And there's another point."

"Which is?"

"This planet is the only source for human brains," she said, and his belly tightened. How odd, he thought distantly. Even while he'd been noticing the blind spot in her thinking, there had been one in his own.

"Of course," he murmured. "If he wants more Trolls-"

"Exactly." She nodded grimly, her eyes hard in the sunlight. "You're right-we can't assume he won't opt for simply wiping us, but I don't think he will. Not anymore. On the other hand, there's one thing I am sure of. If he can't take over, he'll settle for destroying us."

"Which means he'll set up a fallback of some sort," Aston agreed.

"Exactly," she said again, and slammed her fists together in an uncharacteristic gesture of frustration. "Damn. Damn! This makes it even worse, in a way. We've got to get help as quick as we can, Dick!"

"I know." He looked up at the sails and felt the wind. "In fact, I think we can probably shake out one of those reefs. Come on."