"We've all done it," said Meline, a planetologist Herat had worked with before. "But you don't go down to the shoreline! You stand at the top of the ladder. That way you can slam the hatch before it gets too close." Her voice slightly emphasized the word it.

"All right," said Michael. "I'll fetch him in." He clattered up the next flight of steps, to the suit room. It took two precious minutes to get into his quarantine suit, then another to walk through the scouring jets that removed all trace of Earthly microbial life from the suit's surface. He paced clumsily to the airlock and when it finally released him into the bottom of the ladder well he wondered if he was too late. The bore would arrive any minute now.

He pulled himself out of the well into Kadesh's sunshine.

Kadesh's one moon was much bigger and closer to the planet than Earth's Luna. The tides here were orders of magnitude higher; there were few coastal areas that had not been pounded into gentle inclines by millions of years' worth of tsunamis. Here at the shoreline of the largest continent, Michael could have waded two kilometers out to sea before the water came above his waist. The flat vista was deceptively calm, the air blue with towering pillow clouds.

Any second now a wall of water three hundred meters high would come racing over the horizon, carrying with it a froth of boulders as big as houses. Michael had seen it on video; it was over almost before your eye told you what it was.

The scientist was hunkered down in the very shallows, a gloved hand swishing in the water.

Michael jumped as horns sounded from behind him. The sound was urgent, the kind that might have heralded an attack from the air in centuries past. "Doctor Herat?" Michael's voice sounded loud in his own earphone, but somehow he couldn't bring himself to voice the urgency he felt. It would violate the pact of propriety he and the doctor shared. "You'd better get in here, sir. Tide's almost on us."

"I know." Dr. Herat sounded tired. He stood up slowly (reluctantly?) and began walking along the shoreline. He was a tall, rangy man, his angular frame somewhat softened by the quarantine suit. He didn't look at Michael, but continued to gaze out at the regular pattern of rounded shapes half-visible beneath the waves.

It looked from here like gray diamond-shaped bricks, each about forty centimeters across, paved the coastal floor for many kilometers. Long tongues of the same substance reached up the sandy shore. Herat's team had been observing them for weeks and they had seen the transformation that was about to take place, but only on-screen.

Michael watched him warily. Dr. Herat was coming back, but slowly. Maybe he just wanted to see the transformation with his own eyes.

Dr. Herat walked up the low rise that led to the bunker and paused when he was close enough to dash to the entrance, but far enough away that he had a good view of the shore. Then he sat down on a rounded boulder.

Michael loped down to stand over him. "Sir! What are you doing? It's almost on us!"

"We can make it in time from here," drawled Herat. "I just want to see it come in."

This was so totally out of character that Michael found he had nothing to say. There was a brief silence, as they both stared out over the ocean.

Michael forgot the tidal threat momentarily as he saw the well-ordered tile pattern beneath the water swirl and change. In the space of a few seconds a tumult of activity rolled in from the deeper sea; some of the «bricks» retracted into the sand, while others rose. The pattern was different every time, but it always involved long walls and trenches whose exact spacing and orientation was determined by the strength and velocity of the incoming tidal bore.

Dr. Herat sighed. "We know what is happening out there, and we know why; but we haven't got a clue how." He squinted up at Michael. "I never really believed it before, but you know, Michael, I don't think we'll ever fully understand that."

He turned back to the strange vista. "But it is beautiful," he said quietly.

Outside the narrow frame of the video, the full sight was astonishing. The entire ocean floor had come to resemble an Oriental carpet, its detailing done in raised or lowered shells. The photosynthesizing creatures known as Kadists— neither animal nor plant— that grew these armored domes had acted as one entity over an area of many kilometers. What's more, they had crafted a diffraction grating out of their own bodies. The tidal bore would hit this and shake itself to pieces because of the resonances it set up. Nutrients that would otherwise have been carried many kilometers inland to be deposited on the lifeless deserts of the continent, would instead fall straight down to nurture the living plain that had stopped the tidal wave.

Something glinted in the distance. "Doctor! Now!" Michael took Herat's arm as a white line appeared on the horizon. It thickened by the second. So far, there was no sound.

Herat looked up, sighed and levered himself to his feet.

Michael took his arm and they ran for the bunker's hatch. It was farther away than he'd estimated. As Michael ran the last ten meters he could hear a rising roar behind him. Still, he did his duty and made sure Dr. Herat was first down the hatch. Michael himself didn't look back until he had his hands on the ladder.

A cliff of white water rose above him. Deep inside it emeralds shone.

He ducked down and slammed the round hatch. The next instant, the hatch was hit by something massive. Michael nearly fell down the ladder. Dr. Herat was waiting for him at the bottom.

"That was idiotic, sir. What were you thinking?"

"I knew what I was doing." Dr. Herat, who seldom smiled lately, was grinning like a fool. Michael glowered at his employer, but he was too puzzled right now to say more.

Above and around them a deep vibration rattled the fixtures. Still smiling, Dr. Herat put his hand on the wall. They could always feel the strength of the tidal bore through the metal of the station.

"It's got a rhythm to it," said the scientist, "an almost musical one. The AI can't figure out how the Kadists know what patterns to craft: those gray lumps have a better mental model of local conditions than we do."

"Sir, why did you stay so long?"

"I thought… maybe we've been missing the essential experience by just not being out there. We hide in our holes and poke our instruments out and then we try to imagine what it's like for them." Herat shook his head as he walked to the decontagion chamber. "We're not learning anything."

"This isn't about the Kadists, is it," said Michael to his retreating back. "It's about your report to the High Commission."

Herat didn't answer, but his pace faltered for a second as if he were about to turn and say something. He kept going into the bleach shower, where further conversation became impossible.

By the time they met in the station's observation lounge, Meline, Harp, and the others were well into their analysis of the latest bore. The station was now drowned under several hundred meters of ocean and, outside, the Kadists would be sifting through the flotsam that had settled on them. When the tide went out, they would funnel the excess mud and stones into the deep sea again.

"Welcome to the Topside Club," Hart said to Dr. Herat with a grin. "And you even managed to get Bequith to join you." He smirked at Michael, who simply crossed his arms and watched Herat.

Dr. Herat was looking very tired. He didn't return Hart's smile, but spoke to Meline. "Any word on the supply ship?"

"It's in orbit," she said. "But it's got company— a military cruiser."

Dr. Herat sent Michael a puzzled look. He shrugged in reply; this was the first he'd heard of it. "That's funny," said Herat. "Um, any reply to my report?"