“Why inertia-less, Jeanie?” said McAndrew after a few minutes.

Maybe he hadn’t been listening after all. “So we can use high accelerations. So we can get people to go at the same speeds as the unmanned probes. They’d be flattened at fifty gee, you know that. We need an inertia-less drive so that we can stand that acceleration without being squashed to a mush.”

“But that’s not the same thing at all. I told you that a drive with no inertia isn’t possible — and it isn’t. What you’re asking for, now, it seems to me that we should be able…”

His voice drifted off to nothing, he stood up, and without another word he left the cabin. I wondered what I’d started.

If that was the beginning of the McAndrew drive — as I think it was — then, yes, I was there at the very beginning.

So far as I could tell, it wasn’t only the beginning. It was also the end. Mac didn’t talk about the subject again on our way in to Luna rendezvous, even though I tried to nudge him a couple of times. He was always the same, he didn’t like to talk about his ideas when they were “half-cooked,” as he called it.

When we got to Luna, McAndrew went off back to the Institute, and I took a cargo out to Cybele. End of story, and it gradually faded from my thoughts, until the time came, seven months later, for the next run to Titan.

For the first time in five years, McAndrew didn’t make the trip. He didn’t call me, but I got a brief message that he was busy with an off-Earth project, and wouldn’t be free for several months. I wondered, not too seriously, if Mac’s absence could be connected with inertia-less spaceships, and then went on with the cargo to Titan.

That was the trip where some lunatic in the United Space Federation’s upper bureaucracy decided that Titan was overdue for some favorable publicity, as a thriving colony where culture would be welcomed. Fine. They decided to combine culture and nostalgia, and hold on Titan a full-scale, old-fashioned Miss Mister Universe competition. It apparently never occurred to the organizers — who must have had minds that could not see in straight lines, let alone around corners — that the participants were bound to take the thing seriously once it was started. Beauty is not something that good-looking people are willing to take lightly. I had the whole Assembly filled with gorgeous, jealous contestants, screaming managers, horny and ever-hopeful newshounds from every media outlet in the System, and any number of vengeful and vigilant wives, lovers and mistresses of both sexes. On one of my earlier runs I took a circus and zoo out to Titan, but that was nothing compared with this trip. Thank Heaven that the ship is computer-controlled. All my time was spent in keeping some of the passengers together and the rest apart.

It also hadn’t occurred to the organizers, back on Earth, that a good part of the Titan colony is the prison. When I saw the first interaction of the prisoners and the contestants I realized that the trip out to Titan had been a picnic compared with what was about to follow. I chickened out and went back to the ship until it was all over.

I couldn’t really escape, though. When it was all over, when the winners had finally been chosen, when the protests and the counter-protests had all been lodged, when the battered remnants of the more persistent prisoners had been carried back to custody, when mayhem was stilled, and when the colonists of Titan must have felt that they had enjoyed as much of Inner System culture as they could stand for another twenty or thirty years, after all that it was my job to get the group back on board again, and home to Earth without further violence. The contestants hated their managers, the managers hated the judges, the judges hated the news media, and everyone hated the winners. It seemed to me that McAndrew may have had advance information about the trip, and drawn a correct conclusion.

I would like to have skipped it myself. Since I was stuck with it, I separated the Sections of the Assembly as much as I could, put everything onto automatic, and devoted myself to consoling one of the losers, a smooth-skinned armful from one of the larger asteroids.

We finally got there. On that day of rejoicing, the whole ghastly gaggle connected with the contest left the Assembly, I said a lingering farewell to my friend from Vesta — a most inappropriate origin for that particular contestant — and settled back for a needed rest.

It lasted for about eight hours. As soon as I called into the Com Center for news and messages, I got a terse summons on the com display: GO TO PENROSE INSTITUTE, L-4 STATION. MACAVITY.

Not an alarming message, on the face of it, but it worried me. It was from McAndrew, and I doubt if three people knew that I had given him that nickname when I found he was a specialist on theories of gravity (“Old Possum’s Book Of Practical Cats” didn’t seem to be widely read among Mac’s colleagues).

Why hadn’t he called me directly, instead of sending a com-link message? The fact that we were back from Titan would have been widely reported. I sat down at the terminal and placed a link to the Institute, person-to-person to McAndrew.

I didn’t feel any better when the call went through. Instead of Mac’s familiar face, I was looking at the coal-black complexion of Professor Limperis, the head of the Institute. He nodded at me seriously.

“Captain Roker, your timing is impressive. If we had received no response to Professor McAndrew’s coded message in the next eight hours, we would have proceeded without you. Can you help?”

He hesitated, seeing my confused expression. “Did your message tell you the background of the problem?”

“Dr. Limperis, all I’ve had so far is half a dozen words — to go to the L-4 branch of the Institute. I can do that easily enough, but I have no idea what the problem is, or what use I could possibly be on it. Where’s Mac?”

“I wish to God I could answer that.” He sat silent for a moment, chewing on his lower lip, then shrugged. “Professor McAndrew insisted that we send for you — left a message specifically for you. He told us that you were the stimulus for beginning the whole thing.”

“What whole thing?’’

He looked at me in even greater surprise. “Why, the high acceleration drive — the balanced drive that McAndrew has been developing for the past year. McAndrew has disappeared testing the prototype. Can you come at once to the Institute?”

The trip out to the Institute, creeping along in the Space Tug from Luna Station, was one of the low points of my life. There was no particular logic to it — after all, I’d done nothing wrong. But I couldn’t get rid of the feeling that I’d wasted a critical eight hours after the passengers had left the Assembly. If I hadn’t been obsessed with sex on the trip back, maybe I would have gone straight to the com-link instead of taking a sleep break. And maybe then I would have been on my way that much earlier, and that would have been the difference between saving Mac and failing to save him…

You can see how my mind was running. Without any real facts, you can make bears out of bushes just as well in space as you can on Earth. All I had been told by Limperis was that McAndrew had left a week earlier on a test of the prototype of a new ship. If he was not back within a hundred and fifty hours, he had left that terse coded message for me, and instructions — orders might be a better word — to take me along on any attempted search for him.

Dr. Limperis had been very apologetic about it. “I’m only quoting Professor McAndrew, you understand. He said that he didn’t want any rescue party setting out in the Dotterel if you weren’t part of it. He said” — Limperis coughed uncomfortably — “we had a real need for your common sense and natural cowardice. We’ll be waiting for you here as soon as you can arrange passage. The least we can do for Professor McAndrew in the circumstances is to honor his wishes on this.”