“I’m sure he did,” said Bryson tartly. “Now perhaps you’ll tell me what a Killing vector is.”

“Well, Mac could tell you a lot better than I can. But a Killing vector is a standard sort of thing in relativity — I guess you never had any training in that. You get a Killing vector when a region of space-time has some sort of symmetry — say, about an axis of spin. And every sort of black hole, every sort of kernel we’ve ever encountered before, has at least one symmetry of that type. So if McAndrew changed the kernel and made it into something with no Killing vector, it’s like no kernel we’ve ever seen. Right, Mac?”

He looked dreamy. The drugs had taken hold. “I took it past the extreme Kerr-Newman form,” he said. “Put it into a different form, metastable equilibrium. Event horizon had disappeared, all the Killing vectors had disappeared.”

“Christ!” I hadn’t expected that. “No event horizon? Doesn’t that mean you get -?”

McAndrew was still nodding, eye pupils dilated. ” — a naked singularity. That’s right, Jeanie, I had a naked singularity, sitting there in equilibrium in Section Seven. You don’t get there by spinning-up — need different method.” His speech was slurring, as though his tongue was swollen. “Didn’t know what would happen if somebody tried to tap it, to use for a drive. Either the signature of space-time there would change, from three space dimensions and one time, to two space and two time. Or we might see the System’s biggest explosion. All the mass coming out as radiation, in one flash.”

It was slowly dawning on Bryson what we were saying. “But just where is Yifter now?” he asked.

“Gone a long way,” I said. “Right out of this universe.”

“And he can’t be brought back?” asked Bryson.

“I hope not.” I’d seen more than enough of Yifter.

“But I’m supposed to deliver him safely to Titan,” said Bryson. “I’m responsible for his safe passage. What am I going to tell the Planetary Coordinators?”

I didn’t have much sympathy. I was too busy looking at McAndrew’s wounds. The fingers could be regenerated using the bio-feedback equipment on Titan, but the lung would need watching. It was still bleeding a little.

“Tell them you had a very singular experience,” I said. McAndrew grunted as I probed the deep cut in his side. “Sorry, Mac. Have to do it. You know, you’ve ruined your reputation forever as far as I’m concerned. I thought you were a pacifist? All that preaching at us, then you send Yifter and his lot all the way to Hell — and good riddance to them.”

McAndrew was drifting far away on his big dose of painkillers. He half-winked at me and made his curious throat-clearing noise.

“Och, I’m a pacifist all right. We pacifists have to look after each other. How could we ever hope for peace with people like Yifter around to stir up trouble? There’s a bunch more of them, a few hours travel behind us. Fix me up quick, Jeanie. I should be tinkering with the other kernels a bit — just in case the other Lucies decide to pay us a visit later…”

“Now,” said the interviewer, “tell us just what led you to the ideas for the inertia-less drive.”

She was young and vulnerable-looking, and I think that was what saved her from a hot reply. As it was, McAndrew just shook his head and said quietly — but still with feeling — “Not the inertia-less drive. There’s no such thing. It’s a balanced drive.”

She looked confused. “But it lets you accelerate at more than fifty gees, doesn’t it? By making you so you don’t feel any acceleration at all. Doesn’t that mean you must have no inertia?”

McAndrew was shaking his head again. He looked pained and resigned. I suppose that he had to go through this explanation twice a day, every day of his life, with somebody.

I leaned forward and lowered the sound on the video unit. I had heard the story too often, and my sympathies were all with him. We had direct evidence that the McAndrew drive was anything but inertia-less. I doubt if he’ll ever get that message across to the average person, even though he’s most people’s idea of the “great scientist,” the ultimate professor.

I was there at the beginning of the whole thing. In fact, according to McAndrew I was the beginning. We had been winding our way back from the Titan Colony, travelling light as we usually did on the inbound leg. We had only four Sections in the Assembly, and only two of them carried power kernels and drive units, so I guess we massed about three billion tons for ship and cargo.

Halfway in, just after turnover point, we got an incoming request for medical help from the mining colony on Horus. I passed the word on to Luna Station, but we couldn’t do much to help. Horus is in the Egyptian Cluster of asteroids, way out of the ecliptic, and it would take any aid mission a couple of weeks to get to them. By that time, I suspected their problem would be over — one way or another. So I was in a pretty gloomy mood when McAndrew and I sat down to dinner.

“I didn’t know what to tell them, Mac. They know the score as well as I do, but they couldn’t resist asking if we had a fast-passage ship that could help them. I had to tell them the truth, there’s nothing that can get out there at better than two and a half gees, not with people on board. And they need doctors, not just drugs. Luna will have something on the way in a couple of days, but I don’t think that will do it.”

McAndrew nodded sympathetically. He knew that I needed to talk it out to somebody, and we’ve spent a lot of time together on those Titan runs. He’s working on his own experiments most of the time, but I know when he needs company, too. It must be nice to be a famous scientist, but it can be lonely travelling all the time inside your own head.

“I wonder if we’re meant for space, Mac,” I went on — only half-joking. “We’ve got drives that will let us send unmanned probes out at better than a hundred gees of continuous acceleration, but we’re the weak link. I could take the Assembly here up to five gee — we’d be home in a couple of days instead of another month — but you and I couldn’t take it. Can’t you and some of your staff at the Institute come up with a system so that we don’t get crushed flat by high accelerations? A thing like that, an inertia-less drive, it would change space exploration completely.”

I was wandering on, just to keep my mind off the problems they had out on Horus, but what I was saying was sound enough. We had the power on the ships, only the humans were the obstacle. McAndrew was listening to me seriously, but he was shaking his head.

“So far as I know, Jeanie, an inertia-less drive is a theoretical impossibility. Unless somebody a lot brighter than I am can come up with an entirely new theory of physics, we’ll not see your inertia-less drive.”

That was a pretty definitive answer. There were no people brighter than McAndrew, at least in the area of physics. If Mac didn’t think it could be done, you’d not find many people arguing with him. Some people were fooled by the fact that he took time off to make trips with me out to Titan, but that was all part of his way of working.

If you deduce from this that I’m not up at that rarefied level of thought, you’re quite right. I can follow McAndrew’s explanations — sometimes. But when he really gets going he loses me in the first two sentences.

This time, his words seemed clear enough for anyone to follow them. I poured myself another glass of ouzo and wondered how many centuries it would be before the man or woman with the completely new theory came along. Sitting across from me, Mac had begun to rub at his sandy, receding hairline. His expression had become vacant. I’ve learned not to interrupt when he’s got that look on his face. It means he’s thinking in a way that I can’t follow. One of the other professors at the Penrose Institute says that Mac has a mind that can see round corners, and I have a little inkling what he means by that.