“You mean, a new force? Something like discovering gravity for the first time?”

“That will do nicely. We happen to have been aware of gravity for as long as humans existed, and we’ve had theories of it for over five hundred years. We’ve known the electromagnetic force for three centuries, and the strong and weak forces that govern nuclear interactions for just a couple. But gravity is actually a very weak force, something we only feel because very large bodies are involved. Suppose that we had evolved as tiny creatures, no bigger than fleas, in the middle of an energetic plasma? Then gravity wouldn’t have much immediate effect on our lives. We’d have learned about electromagnetism early, but we might still not know about gravity.”

I was finally getting the head-swirling buzz that usually accompanied a McAndrew explanation. “But we didn’t evolve smaller than fleas, in the middle of a plasma.”

“No. But different environments make it easy to detect different forces.”

“But less than a year ago you were telling me that the place to look for new laws of nature is out in deep space where we’ve never been, out where the sun and planets don’t interfere with observations.”

“I did say that. But suppose I’m wrong. Wouldn’t that be exciting, Jeanie? A new law of nature, sitting there under our noses all this time, and detectable down on the surface of Earth.”

And there you had it. Most people hate to learn that they are wrong. Not McAndrew. When he’s proved wrong, he’s ecstatic. It means he’s learned something new, and that’s his main reason for existence.

But I still hated the idea that he’d be going to Earth. “This Ernesto Kugel. If he’s in the Energy Department, that means he works for Anna Griss.”

“So?”

“Do you know him?”

“Not personally. But I know his work, very well. Ernesto Kugel built the Geotron.”

Capital letters again. I resisted the urge to be distracted by that. “Is he the sort of person you believe might make a fundamental new discovery?”

“Oh, no.”

“Well…”

“Not him. He’s an engineer — and a first-rate one — but he’s no physicist. Someone in his lab would have done the work. Someone I don’t know. Kugel would probably put his own name on the report just to make people pay attention.”

“But surely you don’t think that some total unknown would have come up with a big scientific breakthrough?”

“Jeanie, the big breakthroughs always come from some total unknown. And genius can pop up anywhere. Kugel got lucky.”

“Maybe. But Kugel works for Anna Griss, and she hates your guts. Don’t you remember what you did to her?”

“Ah, away with you.” He ran his fingers through his thinning hair. “Jeanie, I’m sure that’s all long forgotten. The invitation to visit Kugel’s lab was approved by Anna. She signed off on it.”

“Did she?” I said. “Well, of course that makes everything fine, doesn’t it?”

I should have known better. Irony is totally wasted on McAndrew.

He beamed at me. “I knew you’d see it my way when you had the facts, Jeanie. How soon can we leave?”

I think my inner voices are pretty good when it comes to warning of trouble. The problem is, I don’t always listen to them.

This time I allowed another event to occupy my mind when I ought to have been worrying about McAndrew’s visit to Earth. In my own defense, I must say that the intrusion came from outside. When the linked spheres of the Assembly were halfway to Earth, with Mac and me cozy in the Control Section, I received a message from Hermann Jaynsie at the United Space Federation Headquarters.

It was long and wordy, because Hermann is long and wordy, but I can boil it down. It said, in essence, “What the devil did you do, Captain Roker, on your last cargo haul from the Jovian system to Earth? We thought we had a deal with them for four billion tons of vegetable foodstuffs, grown in our Europan ocean farms. Now Earth is telling us they don’t want to take delivery of any more shipments.”

The lightspeed round-trip travel time to USF Headquarters was seven minutes, so I couldn’t exactly chitchat back and forth. But I did send him a pretty long reply, which again can be boiled down to, “Damned if I know, Hermann. They seemed happy enough with what I dropped off last time.”

My livelihood wasn’t hurt by the cancellation of a food supply contract with Earth; but my ego was, and I spent a good deal of time fuming. Was it Anna Griss, getting at me in a remarkably indirect way? I knew she was capable of subtle malice. But I still looked for a more logical explanation. I couldn’t see even Anna risking Earth’s food supply just to get at me.

I had no intention of going to Earth, or wasting another minute thinking of Ernesto Kugel and his mysterious invariant. So when we arrived at the Colony drop-off point, where the Assembly would be moored until its next trip out, McAndrew and I went our own ways. He headed down on a shuttle, as excited as a child on his way to a birthday party. I mothballed the ship, and handed it over to the local USF maintenance crew.

That took me three days. And then on the fourth morning, without thinking about what I was doing, I found myself aboard a shuttle vessel.

Heading for Earth.

I had been given a number to reach McAndrew, and I forwarded a message to tell him that I was on the way, and when and where I would arrive. I didn’t ask, but I rather hoped he might be waiting for me.

He wasn’t. And it was one of life’s less pleasant experiences to pass through entry formalities, search for Mac’s face, and see Van Lyle waiting for me on the other side of the barrier.

“Captain Jeanie Roker.” He reached out and took my hand. “It’s been a while.”

I shook his hand, but my feelings must have showed on my face, because he laughed and said, “Don’t say anything. You did what you did, and I thoroughly deserved it. Let bygones be bygones.”

But he touched his fingertips to his bent nose.

I said, “McAndrew—”

“Is having too much fun, Captain, to tear himself away from the Geotron facility. He asked me to come to the port, and take you there to join him.”

It sounded awfully plausible. But I couldn’t put the past behind me as easily as he claimed to have done. “Professor McAndrew asked you to come and meet me?”

Instead of answering, Lyle took a palm-sized phone from his pocket and tapped in a string of numbers. “Four one seven,” he said into the unit. After a few seconds’ pause he handed me the phone.

I found myself staring into the tiny screen at a familiar high-cheekboned face. His wispy hair was sticking up in little random spikes, and his color was a fraction ruddier than usual. I couldn’t see his fingers, but I could bet that he was cracking the joints.

“Jeanie,” he said, as soon as he saw me. “I didn’t expect to hear from you until you arrived at the Geotron. What’s wrong? Are you having problems getting underwater?”

Underwater? But it was McAndrew, without a doubt. McAndrew live, healthy, unrestrained, and by the look of it having the time of his life. He actually did not sound too thrilled by the news of my arrival.

“No problems,” I said. “I touched down just a few minutes ago.”

“Right then. I’ll have to go. We’re very busy here.” And his picture promptly vanished. The phone link disconnected.

That was the genuine McAndrew, without a doubt, and he was clearly all right. The smart thing to have done at that point would have been to apologize to Van Lyle for my rudeness, plead prior job commitments off Earth, and turn right around and head back to space. Instead I handed the little phone back, sighed, and said, “Before I make a complete fool of myself, tell me one thing. What is a Geotron, and where is a Geotron?”