A fan in the back of his helmet changed pitch, adjusting to temperature or humidity.

His one major political drawback was that he was a bachelor. The party believed the voters would not be comfortable without a first lady. That notion did not show up in surveys, but it was the common wisdom in a society that had become increasingly concerned about personal morals while only one marriage in six now stayed the course.

The ground was gray and crumbly. The guidebooks maintained the Moon hadn't changed much in three billion years or so. There was no volcanism on Luna, no climate, no wind to move things around. It was a world where nothing ever happened except occasionally it got plunked by a falling rock.

He climbed back up on the walkway and looked around at the flat plain. "I thought Moonbase was inside a crater," he said.

Evelyn was behind him, allowing him an unbroken view. "It is. But the crater's big, and the Moon's small. Alphonsus is a hundred seventeen kilometers across. We're in the center of the crater, and its walls are all below the horizon. But they're there. If you like, we can take a ride over."

"Yes," said Charlie. He studied her for a long moment, wishing he could see her face. "You'd like to do that, wouldn't you?"

She chuckled. "I think you caught me," she said. "But yes. With the vice president's permission, we can turn this into a jaunt."

"By all means," said Charlie. He looked at the horizon. "I wonder if we can see the comet from here."

Evelyn was silent, and the voice of the technician came over the radio. "No, sir, it's not visible from Moonbase."

"Pity," he said.

Beaver Meadow Observatory. 9:30 A.M.

Wesley Feinberg canceled his flight home and stayed on at Beaver Meadow. Hoxon gave him an office and a computer and he got on the circuit with Kitt Peak and NASA and Zelenchukskaya and twenty other institutions. The astronomical community, of course, was fully aroused and scrambling to pin the comet down. Could it be identified with anything in the record? How big was it? Where was it going?

The quick way to get a handle on the object was to track down where it had been, say, in January or February. Then it would become possible to work out a trajectory. It should have been visible in the early part of the year. So it was just a matter of conducting a thorough search.

But as yet there was insufficient data to make even an intelligent guess where it might have appeared in the winter heavens. Feinberg worked methodically, bringing up sections of sky and comparing them against the database, hoping to find an object that did not belong. The images were produced by ACCDs, Advanced Charge-Coupled Devices, mounted on major telescopes around the world and in orbit. The pictures were far sharper than the photos with which he'd worked when he'd begun his career near the end of the last century.

He knew that an army of professionals and talented amateurs were doing the same thing, but he wasn't interested in waiting for someone else's results. Although he'd have denied it, he was a competitor and wanted very much to get there first. He was, after all, less likely to be led astray by every point of light that didn't fit the catalog. But after working through the night, he had nothing. That was understandable. What he did not understand was that no one else had anything either.

Feinberg had stayed with it until almost six A.M., when he began to doze at the keyboard. Finally he'd given up and commandeered a couch in a utility room, where he slept until noon. By then several sites had reported positives. But after a glance Feinberg dismissed their "finds" as the carcasses of junked earth satellites, two known asteroids, and in one case, a nebula.

By late afternoon there was still nothing.

Curious. "It's very hard to understand," he told Hoxon, who had done some nominal searching on his own.

The director agreed. He was a garrulous, beak-nosed man who spent most of his time organizing public tours and who seemed to have remarkably little interest in real astronomy. He persisted in carrying on pointless conversations with people around him who were trying to work.

Feinberg extended his search, on the theory that the comet might be moving substantially faster or slower than the forty kilometers per second that was more or less the ballpark velocity. He worked through the late afternoon, sorting images while the mystery grew.

At six P.M. a postdoc at Cerro La Silla in Chile asked for help. She sent pictures that seemed to indicate she'd found a second comet. The pictures revealed an object on the far side of the Sun, out near Jupiter's orbit. The images had been run on successive nights, March 25 and 26. But the same area in another set of images taken six days earlier showed nothing. Nor did the object appear in a third series beginning March 30. The object had apparently been in the sky for ten nights at most and then vanished. Where had it gone? The postdoc was asking if anyone else had pictures of the area during the subject period.

Now, that was odd. They had two elusive comets.

Hoxon appeared and suggested Feinberg join him for dinner. "My treat," he said.

Astronomers do not, as a rule, command large paychecks. Consequently, Feinberg wasn't surprised when Hoxon took him to the local Shoney's. They talked about the Chilean business. In fact, Feinberg knew he was babbling about it. But Hoxon's only significant response was to observe that it was only a postdoc after all, and who knew what she really saw.

We've got the pictures, nit. But Feinberg let it go.

ACCDs functioned by counting photons and converting the results to optical images. Feinberg began thinking about photon counts and fingerprints somewhere between the meat loaf and the ice cream sundae he decided he deserved. Two objects, one near Jupiter, one near the Sun. Both hard to track.

He did a quick calculation to check the idea that had been unconsciously forming, and smiled at the result. He'd been scribbling on a napkin, and when Hoxon asked him what it was about, he shrugged. "Nothing," he said, dismissing his result.

His host did not think it was a good idea to go back to work, announced that he was going home, and suggested that Feinberg also quit for the night. Feinberg wondered what would have happened to the spirit of scientific inquiry if everyone had possessed the director's driving curiosity. "No," he said, "I have one or two things to finish up."

Unfortunately, what Feinberg wanted to finish up couldn't be handled directly from his keyboard. He made two phone calls. The first was to the Skyport Orbital Laboratory, which had used its Venusian probe to make the images of Tomiko's Comet; and the other was to Cerro La Silla. In both cases he asked for the photon count that had produced the comet images. Both sites said they would get back to him.

Cerro La Silla returned his call within the hour. He recorded the result and waited eagerly for the response from the Orbital Lab. It was a procedure that could take time, especially if they were busy, as he suspected they were. At midnight he was still sitting by his phone.

He didn't recall dozing off, but he remembered coming out of a deep sleep, seeing gray light coming through a window, uncertain at first where he was. The telephone was ringing.

Windy Cross at Skyport apologized for the delay, but gave him the data. "If you don't mind, Professor," asked Windy, "what use is it?"

Feinberg remembered the count from the Jupiter comet. It was almost identical. Not definitive, but damned near. They were possibly the same object. "I'll get back to you, Windy," he said. "When I'm sure."

He stared at the numbers, puzzling over the problem. The Cerro La Silla sighting was way the hell out of range. Comets had an upper speed limit of about fifty kps. If this was the same object, it would have to be moving at eight or nine times that velocity. Four hundred-plus kilometers per second!