Lou wished them good luck and said he was sorry to see them leave so soon. He reminded Valya that she was not permitted to start her engines until the facility gave her an all clear.

He escorted them back to the boarding area. Minutes later, while they strapped in for another gravity launch, the moonrider began to withdraw from the monitor. By the time they were ready to go, it had almost vanished.

The departure was more harrowing than the docking procedure had been, because the forward area went down, and the chair MacAllister was using faced the bridge, which rotated until it was straight down and he was hanging by the harness.

Gradually, the effect went away, and they were able to move around again. But it was a long, slow flight out to the point at which they received permission to ignite their engines.

VALYA INFORMED UNION Operations that the Salvator was on its way back to Ophiuchi. Five hours later she had a response from the watch officer: “Exercise caution. Keep us informed.”

The monitor passed along its analytical data, such as it was: Moonrider drive unit unknown. Light source unknown. Attitude thrusters detected. And sensing devices. Unintelligible symbols on the hull. “It appears to move by casting and manipulating gravitational fields.”

“That sounds a little bit like what we were doing,” said MacAllister.

Valya agreed. “Except we wouldn’t be able to do it from inside the ship. At least not if we wanted to pick up any velocity.”

Finally, they made their jump and began the long cruise through the fogbanks. Meantime the monitor stayed silent.

Previously, they had passed their time more or less as individuals. Eric enjoyed reading mysteries, and he’d already gone through three. Amy alternated between homework and games. MacAllister worked on his notes or read. Valya disappeared onto the bridge for long periods, during which they could hear the soft beat of Greek music.

There was an inclination now, perhaps in the presence of the moonrider, to draw together. They played a four-handed game of snatchem, talked about what they would do when they got home, broke for a meal, and decided to do a musical.

They let Amy make the call, and she chose Manhattan, the story of the fabled alcoholic song writer Jose Veblen, and his alternately inspirational and destructive romance with the singer Jeri Costikan. They apportioned the roles, with Eric playing Veblen and Valya as Jeri. Amy played Jeri’s best friend (and better self), while MacAllister portrayed Veblen’s long-suffering agent.

During the showstopper at the end of the first act, which featured Amy’s and Valya’s characters, accompanied by the cast at large, singing and dancing their way through “Y’ Gotta Let Go,” the monitor reported a second sighting at Ophiuchi.

Valya killed the show, and Bill provided a picture. “It’s moving across the monitor’s field of vision,” Bill said. “Range is eight hundred kilometers.”

“There’s nowhere to go in that system,” said Eric. “What’s the point? Are they just riding around?”

MacAllister laughed. “You’d think, if they were really intelligent aliens, they’d have something more important to do than hang around out there all day.”

“Apparently not,” said Valya. She looked at Amy. “What’s so funny?”

“Maybe they’re kids.”

“It’s braking,” said Bill.

MacAllister leaned forward and propped his chin on his hands. “Maybe it’s coming back to have another look at the monitor?”

“I don’t think so,” said Valya. “It’s not going in the right direction.”

Amy was completely oblivious to anything but the screen. She got in front of MacAllister and momentarily blocked his view. “There’s another one out there,” she said. “See? Beside it.”

There was indeed a second moving object. But it was star-like.

“That is odd,” said Bill. “If it’s another moonrider, the monitor hasn’t reported it as such.”

“It’s something else,” said Valya.

The monitor’s telescope belatedly focused on it.

“Asteroid,” said Amy.

Eric nodded. “No question about it.”

Bill appeared in the entry to the bridge. He reminded MacAllister of a physics professor, gray beard, rumpled jacket, distracted eyes. “The moonrider is shedding velocity,” he said.

Valya was seated beside MacAllister. She put a hand on his forearm. “It’s going to land on the thing.”

The monitor’s onboard AI apparently drew the same conclusion, and ratcheted up the magnification. The asteroid was misshapen, nondescript, doing a slow tumble. “It’s nickel-iron,” said Bill. At first the globe looked bigger than the rock, but as it moved closer it began to shrink until it was in fact minuscule in contrast. “The asteroid is approximately two kilometers in diameter.”

The moonrider settled like a dark insect onto the surface.

There was a series of ridges near one pole, and something had sliced a deep crevice through them. “What could it possibly want with that thing?” asked Amy.

Valya shook her head. Wait and see.

It snuggled into the crevice. And became imperceptible. Then it reddened, glowed, and faded. And again. Like a heartbeat. “This is where it would be helpful,” said MacAllister, “if the monitor had a drive unit of some sort.”

“Costs too much,” said Valya.

They waited for something to happen.

And waited.

The asteroid continued its slow tumble. The moonrider brightened and dimmed. The picture was becoming smaller, as the asteroid, with its cargo, moved farther from the monitor’s telescope.

MacAllister’s imagination ran wild. Maybe the asteroid was a base? The moonrider might be attached to a boarding tube.

“What would they be doing with a base in a godforsaken place like that?” said Eric.

MacAllister hadn’t realized he was thinking aloud.

“Maybe they use it for refueling,” Amy said. “Or recharging.” She turned to Valya. “Is that possible?”

“Anything’s possible,” she said. “We just don’t know enough yet.”

“Valya.” Bill sounded surprised. “The asteroid’s changing course.”

“How do you mean?”

“It’s being diverted. Turning.”

“Turning where?” demanded MacAllister.

“Too soon to tell.”

Valya looked frustrated. “I wish we were a little closer.”

Eric stared at the images, at the constant red pulse inside the depression. At the sheer size of the asteroid. “It doesn’t look possible.” He turned toward Valya. “It’s too small to move something that big, isn’t it?”

“I would have thought so. But it looks as if it’s doing it.”

“Could we move it?” asked MacAllister.

“A little bit,” she said. “If we had a lot of time. And a way to lock on to it. But not like this.”

“Monitor reports the asteroid is accelerating.”

Valya looked puzzled. “Maybe it has a project of some sort. The wire weave at Origins was made from asteroids in this system.”

“Maybe that’s what it is,” said MacAllister. “That must be one of our ships.”

“Take my word for it, Mac. It isn’t — ”

“Uh-oh,” said Amy.

The moonrider had let go. It lifted from the surface. Began to move away from the rock.

“The moonrider is also accelerating,” said Bill.

“Bill,” said Valya, “will you be able to find it when we get there?”

“The moonrider? Or the asteroid?”

“The asteroid.”

“Sure,” he said. “If it doesn’t change course again.”

Amy looked entranced. The visitors, whoever they were, had actually shown up. Mac had not believed for a minute that anything like this could happen. It was all he could do not to cheer.

He watched the moonrider fade out among the stars. Listened to Bill’s report: “The asteroid remains in a solar orbit. It’s moving toward the sun, but I can’t see that it’s going anywhere in particular.”

“You’re sure?”

“Keep in mind this is a preliminary analysis. But yes, they’ve adjusted the orbit somewhat, but to what purpose I have no idea.”

THE ACTION APPEARED to be over for the night. MacAllister treated himself to a snack, went to bed, and slept peacefully. In the morning he woke with a fresh perspective. For decades, experts had been predicting that advanced aliens would be hard to understand. And they’d used the creators of the omega clouds as a case in point. The clouds had rolled through the galaxy, or at least the Orion Arm of it, causing mindless destruction with mathematical precision. Nobody knew why. Hutch had a harebrained theory about creating art, but MacAllister had drawn a different explanation. The aliens were game-playing. They sent out the clouds, sat back, and kept score. Whoever got the most explosions won.

Maybe the same sort of thing was happening with the moonriders. Or maybe they were conducting an exercise of some sort. Testing, for example, their capability to move asteroids around.

The hypothesis we would have serious problems communicating with alien civilizations was likely to prove true. But not necessarily because the aliens were subtle and sophisticated and simply products of a radically different culture. Rather it might be that the aliens, by any reasonable standard, were deranged. Dummies with big toys invented by somebody back home. Somebody who was too smart to get out and ride around between the stars himself. The idiots always rose to the top and made policy.

It explained a lot of things.

WHEN HE WANDERED into the common room, nothing had changed. There’d been no more moonriders, no visitations with other asteroids, no indication of anything out of the ordinary.

The asteroid had receded, and was now only a dim reflection at high mag.

The monitor, meantime, reported that the asteroid’s heading had been changed seventeen degrees laterally. And there’d been a very slight horizontal alteration. It was moving below the plane of its original orbit.

They also had a response from Hutch: “We won’t be able to get a ship out there for several days,” she said. “Take a look at the asteroid. There’s a possibility it’s a base. And I know how that sounds. Nevertheless, see what you can find out but approach with caution.”

A base. MacAllister had been ahead of the curve on that one.

Hutch continued: “Try to determine what they were doing. Again, keep your eyes open. Especially if the moonriders show up again. Do not assume they aren’t hostile. Avoid any close encounter.”

MacAllister laughed. “We’re the defense against a vanguard of alien invaders. If they actually are hostile, Valya, what sort of weapons have we to defend ourselves? Does this thing have any kind of gun? Or missile launcher?”