Quake stood huge in the sky, a sunlit, mottled ball that was poised and ready to crash down onto him. His hindbrain told him that no force in the universe could hold such a weight, that one would never become used to the sight. At the same time his forebrain did a calculation of orbital rates and the matching of centrifugal and gravitational forces, and assured him that everything was in perfect dynamic balance. People might be uncomfortable with the threat of Quake overhead for a day or two; then they would get used to it and ignore it.

From this distance no details were visible, but it was clear that he was looking at a world without major seas and oceans. Rebka thought at once of terraforming; not just Quake or Opal, but of the doublet together. It was the perfect application. Quake had the metals and minerals; Opal had the water. It would be a substantial task, but no bigger than others he had undertaken. And the beginning of the necessary transportation system was already in position.

He looked along the thread of the Umbilical. The line upward was visible for perhaps a hundred kilometers before he lost it. Midway Station, four thousand kilometers above them at the center of mass of the Opal-Quake system, could be seen as a tiny golden knot on an invisible thread. They would be there for changeover in half a day. Plenty of time to think.

And plenty to think about.

Rebka closed his eyes and sorted through his worries.

Begin with Max Perry. After only a couple of days of exposure to the man it was clear that there were two Max Perrys. One was a quiet, dull bureaucrat, someone whom Rebka would expect to find in a dead-end job on any rat-hole world in the Phemus Circle. But somewhere under that there was a second personality, an energetic and subtle person with strong ideas of his own. The second Max Perry seemed to wake only on random occasions.

No, that was wrong. The other Max awoke when Quake was the issue, and only then. And Max II must be the clever and determined man that Perry had been, all of the time, seven years before — when he was assigned to Dobelle.

Rebka leaned back in his seat, physically relaxed and mentally active. So. Accept that there was a mystery in Max Perry. But ask if that mystery justified pulling a senior, action-oriented man like Hans Rebka away from a key project involving exploration of Paradox to become an amateur psychologist on the minor world of Opal.

It did not add up. If the men and women who ran the Phemus Circle were good at anything, it was at conserving resources; and human resources were the most precious of all.

Look for another motive, another reason for his being assigned there.

Rebka was not naive enough to believe that his superiors would tell him the whole story behind his assignments. They might not even know the whole story. He had found that out the hard way, on Pelican’s Wake. A troubleshooter was expected to be able to operate without a full deck, and Rebka functioned best when he was forced to work things out for himself.

Terraforming of Quake and Opal?

His superiors must know that as soon as he saw the planetary doublet of Dobelle he would evaluate both worlds as possible subjects for terraforming. Was that the real reason he had been assigned there? To set in motion that project?

Still it did not feel right.

So add in some of the other variables. Four groups were requesting a visit to Quake at Summertide. He might believe that one was a genuine coincidence — the Alliance Council had no reputation for deceit — but four at once was not plausible.

And the upcoming Summertide would be the biggest ever. Maybe that was the key. They were there for that special Summertide.

Again, it did not feel complete. Darya Lang had told him that she did not know it was to be a specially big Summertide until Perry had told her.

Rebka believed her. But that belief itself was suspect. He had left a woman companion behind him on the station orbiting Paradox. No matter what his brain told him, his glands were probably seeking a replacement. In the first two minutes with Lang he had been aware of an attraction between them. And that must make him more cautious in dealing with her, since he wanted to believe her.

Lang did not know that Opal and Quake were scheduled for monster Summertides. Fine. Believe that, and still it did not mean that she was what she pretended to be. She could have another and more complex role to play.

Was she what she claimed to be? That could be checked. Before he left Starside, Rebka had already sent an encrypted message through the Bose communications net, asking for confirmation by Circle intelligence that Darya Lang was an expert on Builder artifacts. The reply would be waiting when they returned from Quake. Until then, questions regarding Lang had to be put to one side.

But there were plenty of other questions left. Hans Rebka was interrupted by a light touch on his arm. He opened his eyes.

Max Perry was gesturing upward, along the line of the Umbilical. Quake loomed above them, half again as big as when they had started. But at the moment it reflected only the murky dried-blood light of Amaranth. Mandel was hidden behind the planet, and as Summertide approached, its dwarf companion was swinging in closer. Soon night would disappear completely on Quake and Opal.

“What’s happening?” Rebka said. “I thought the Umbilical ran all the way between Opal and Quake.” He should have been a little nervous, because it was sheer vacuum outside the car; but Perry had a smile on his face, and he certainly did not act like a man facing disaster.

“It does,” he said. “We’re approaching the Winch. We have to be shunted here, and reconnected on the other side of Midway Station. Travelers can go into the station if they want to — it’s well equipped, power and food and shelter — but I see no point in that. If you like we can take a closer look at Midway on the way back.”

As Perry spoke, the car they were riding in was swinging away from the main cable and running through a series of gates and connecting rails. Quake had vanished. Midway Station was off to the right. Rebka could see a whole line of ports, any one of them big enough to accept the capsule. He looked back to the place where the main cable of the Umbilical disappeared into bright blue nothingness and then, a few kilometers farther on, reappeared.

“I don’t see any winch.”

“You won’t.” The second Max Perry was back, alert and energetic. “That’s just a name we give it. You see, Opal and Quake are in a near-circular mutual orbit, but their separation distance varies all the time — anything up to four hundred kilometers. A permanent Umbilical can’t work unless you have something to reel in or pay out cable. That’s what the Winch does.”

“That hole in space?”

“Right. It works fine, and at Summertide it reels in extra so that the coupling is lost at the surface of Quake. And it’s smart enough to leave the tether on Opal intact. But it’s all Builder technology. We have no idea where the cable goes to or comes from, or how it knows what to do. People on Quake and Opal don’t care, so long as they can raise or lower the Umbilical through the special control sequences.”

Perry’s reluctance to visit Quake had vanished at liftoff from Opal. He was peering forward as they rounded the bulk of Midway Station, seeking Quake again in the sky ahead.

The capsule moved back to attach to the new length of the Umbilical, and they began to pick up speed. Soon they passed the mass center of the Dobelle system, and there was a clear sense of falling toward Quake, their own centrifugal force adding to Quake’s gravity. The dark planet grew visibly, minute by minute, in the sky ahead of them. They began to see more surface detail.

And Rebka could see another change in Perry. The younger man’s breathing was faster. He was staring at Quake’s approaching surface with rapt attention, his eyes bright and staring. Rebka was willing to bet that his pulse rate had increased.