His right foot connected with something solid. He dropped to all fours on the roof, sliding down backward until his feet caught on the drain. Slipped on that and slithered until his knees lodged briefly in the rain gully.

"Drop, dragonrider," someone below him shouted. "We'll catch you."

Hands tugged at the toes of his boot. He went limp, committed to the downward fall. Instantly his ankles were caught, then hands fastened on his knees, letting him down, supporting his thighs. In the next moment he was on his feet, being congratulated and enthusiastically thumped for the success of his daring stunt.

Made it,he said somewhat smugly to Golanth who was hovering above.

"Thanks! Thanks, thanks!" he said, skewing around to those behind him and then turned to the door. "Benden Weyr's orders," he said to the two guards who were preventing anyone from entering. The crowd behind was bombarding him with a babble of questions. "I'm F'lessan. Lemme in," he shouted above the tumult.

They did, immediately resuming their defensive postures. F'lessan strode forward, wondering how much time that stunt had taken, opening his jacket and peeling the helmet off. She's here,Golanth said. Which she?F'lessan's tone was amused. Both of them. She studies stars, you know,Golanth added. She's shared night watches at Cove Hold.

Then please inform Zaranth that F'lessan requires her rider's assistance in the Interface office.

F'lessan turned back to the door guards. "The Monaco Weyrleader's on his way in." He had to shout to be heard above the babble outside. "See that green rider Tai comes in, too, as quickly as possible." Then to all the others shouting questions, he smiled and waved, saying "We'll sort it all out and report to you shortly."

Monarth said he saw how you got in, F'lessan,and Golanth rumbled with amusement. They'II try it.

Maybe Mirrim will break a leg,F'lessan muttered, feeling uncharitable toward her. As he continued, he nodded in a blithe, unconcerned manner to a knot of anxious men and women at the other end of the reception area and hurried down the right-hand hall to the YokohamaInterface offices.

At the end of that hall, the door to the Aivas chamber was open. He felt the usual grab at his throat when he saw the blank screen that had once given humans access to the most amazing intelligence on Pern. He swallowed the lump and turned left into the room where, seven Turns ago, he had learned how to build a computer.

There had been significant additions to the original office, of course, to deal with all the data sent down from the Yokohama,the one remaining colony ship. Ordinarily the office was pleasantly busy, people at the four banks of workstations that were arranged back-to-back in the center of the large room. Now an odd anticipatory silence dominated the room as all eyes were trained on the wall monitor, which F'lessan couldn't see from the door.

"You can't come-" began the burly door guard, whom F'lessan recognized as Tunge, one of the regular men. He skipped aside and explained with soft intensity. "Sorry, bronze rider, but everyone and his fire-lizard's been trying to get in here since that thing in the sky was spotted." Tunge was impressed, and scared.

F'lessan made a quick survey of those in the room; where was Wansor? Surely Lytol and D'ram had got him here so the phenomenon could be described to him?

"Master Wansor?" he murmured to Tunge.

"Oh, him." With a quick grin, Tunge jerked his head back down the corridor. "Him 'n' Lord Lytol 'n' bronze rider D'ram are in the conference room. There's a big screen there, too, you know, so they could tell him what information's being processed."

Directly across the room, one of the smaller monitors was blinking the legend PHO. F'lessan shook his head, trying to remember what the initials stood for-possibly hazardous object? Why had he assumed that the bright light was a comet? Below the title "Encounter Analysis" were eight columns, headed ESTIMATED TIME TO PERIGEE, DISTANCE, VELOCITY, PROBABILITY, ATMOSPHERE BREAKUP, IMPACT ERROR, LATITUDE, AND LONGITUDE. These were showing numbers that altered rapidly, either decreasing or, in the case of longitude, increasing. As F'lessan watched, the Estimated Time to Perigee ticked over to 5800.

That display gave him another frisson of apprehension. When had that clock started ticking down? He'd come as fast as he could without timing it. But then, he hadn't anticipated that this could be a real crisis.

He inched carefully along the wall, moving people who were almost unaware of being manipulated, so intent were they upon the monitor's reports. He recognized several as off-duty technicians. Being tall, he eased into a spot in the corner and still had a clear view of the monitor. In front of him, Stinar, the duty officer, was standing with the barrel-chested man of medium height, dark-haired, with a handsome hooked nose, whom F'lessan recognized as Erragon, Wansor's assistant. Shouldn't he have been in the conference room? F'lessan chided himself. Lytol and D'ram could explain adequately to Wansor but Erragon was needed in here, interpreting the Yoko'stelemetry. When this was over, he'd undoubtedly report to Master Wansor the more technical details of this unusual occurrence. The two were intent on the visual transmitted to Landing by Yoko.

At maximum magnification, Yokoshowed a small image of the nucleus, embedded in clouds of dust. Yokoadded another window, attempting to trace it back to its original orbit. Details came up as:

Semi-Major Axis = 33.712. Period= 195.734 Eccentricity= 0.971 Perihelion = 0.95 3 AU Inclination = 103.95 degrees.

But F'lessan, knowing all these figures would be available later, concentrated on the comet, now resolving jets and debris. Yes, it must be a comet. That would explain its slowing with respect to the stars. Outgassing can push a comet about, making an estimate of its orbit even harder. Furthermore, with the long axis running from the northwest to the southeast, who could tell? It may skid across our atmosphere and disappear south, thought F'lessan hopefully.

Yet another working window opened, labeled searching. Images of what F'lessan knew to be Pernese space flashed past, the streaking orbits of some of the minor planets against the background of northern hemisphere stars.

"What's all that about?" Stinar asked Erragon who was blinking at the rapidly altering display.

"I'd hazard the guess that it's searching for any old images of the comet. It is possible, you know," Erragon went on, frowning at the speed of the search pattern, "that the comet originated in the Oort cloud." His grin was forced. "It might even have been seen by our Ancestors."

"Really?"

Erragon sighed, flicking his attention to some of the other sidebars. "We have a lot of material to review, you know. Just for our home system. Ah, yes," and he pointed back to the search. "The material we're seeing was released from the comet two to three weeks ago. Here we go," he added, intent on the newest sidebar readings.

Encounter Analysis Estimated Perigee in 1800 seconds Projected Perigee Distance 16km, error± 296km Encounter Velocity 58.48kmsec ± 0.18km/sec Probability of Impact 48.9%

Probability of Atmospheric Breakup (Airburst) 1.3% Impact Error Ellipse 3698 times 592km Location and Orientation of Ellipse 9° north, 18° east, Major Axis bearing 130°

At that point, Erragon visibly tensed, leaning slightly forward on the balls of his feet in an attitude that confirmed F'lessan's bad feelings about the alteration in probability of impact. He wasn't certain that the error ellipse of impact was reassuring. Unless the comet suddenly pulled itself up in an escape parabola. Estimate to Perigee decreasing: 1500 seconds, or 25 minutes, F'lessan told himself. He also didn't like standing around, watching, in a room full of people who didn't seem to realize what could happen. The tension was palpable but everyone was so focused on the screen, too scared to ask questions or to break into the concentration of Stinar or Erragon.