To Shara Zoll, for friendship and everything else. To Kristine and Athena, for their patience and love. 

No one noticed the rock.

And for a very good reason. The rock was nondescript, one of millions of chunks of rock and ice floating in the parabolic orbit of a long-dead short-period comet, looking just like any chunk of that deceased comet might. The rock was smaller than some, larger than others, but on a distribution scale there was nothing to distinguish it one way or another. On the almost unfathomably small chance that the rock was spotted by a planetary defense grid, a cursory examination would show the rock to be composed of silicates and some ores. Which is to say: a rock, not nearly large enough to cause any real damage.

This was an academic matter for the planet currently intersecting the path of the rock and several thousand of its brethren; it had no planetary defense grid. It did, however, have a gravity well, into which the rock fell, along with those many brethren. Together they would form a meteor shower, as so many chunks of ice and rock did each time the planet intersected the comet's orbit, once per planetary revolution. No intelligent creature stood on the surface of this bitterly cold planet, but if one had it could have looked up and seen the pretty streaks and smears of these little chunks of matter as they burned in the atmosphere, superheated by the friction of air against rock.

The vast majority of these newly minted meteors would vaporize in the atmosphere, their matter transmuted during their incandescent fall from a discrete and solid clump to a long smudge of microscopic particles. These would remain in the atmosphere indefinitely, until they became the nuclei of water droplets, and the sheer mass of the water dragged them to the ground as rain (or, more likely given the nature of the planet, snow).

This rock, however, had mass on its side. Chunks flew as the atmospheric pressure tore open hairline cracks in the rock's structure, the stress of plummeting through the thickening mat of gases exposing structural flaws and weaknesses and exploiting them violently. Fragments sheared off, sparkled brilliantly and momentarily and were consumed by the sky. And yet at the end of its journey through the atmosphere, enough remained to impact the planet surface, the flaming bolus smacking hard and fast onto a plain of rock that had been blown clean of ice and snow by high winds.

The impact vaporized the rock and a modest amount of the plain, excavating an equally modest crater. The rock plain, which extended for a significant distance on and below the planet surface, rang with the impact like a bell, harmonics pealing several octaves below the hearing range of most known intelligent species.

The ground trembled.

And in the distance, beneath the planet surface, someone finally noticed the rock.

"Quake," said Sharan. She didn't look up from her monitor.

Several moments later, another tremor followed.

"Quake," said Sharan.

Cainen looked over to his assistant from his own monitor. "Are you planning to do this every time?" he asked.

"I want to keep you informed of events as they happen," Sharan said.

"I appreciate the sentiment," Cainen said, "but you really don't have to mention it every single time. I am a scientist. I understand that when the ground moves we're experiencing a quake. Your first declaration was useful. By the fifth or sixth time, it gets monotonous."

Another rumble. "Quake," said Sharan. "That's number seven. Anyway, you're not a tectonicist. This is outside your many fields of expertise." Despite Sharan's typical deadpan delivery, the sarcasm was hard to miss.

If Cainen hadn't been sleeping with his assistant, he might have been irritated. As it was, he allowed himself to be tolerantly amused. "I don't recall you being a master tectonicist," he said.

"It's a hobby," said Sharan.

Cainen opened his mouth to respond and then the ground suddenly and violently launched itself up to meet him. It took a moment for Cainen to realize it wasn't the floor that jerked up to meet him, he'd been suddenly driven to the floor. He was now haphazardly sprawled on the tiles, along with about half the objects formerly positioned on his workstation. Cainen's work stool lay capsized a body length to the right, still teetering from the upheaval.

He looked over to Sharan, who was no longer looking at her monitor, in part because it lay shattered on the ground, near where Sharan herself was toppled.

"What was that?" Cainen asked.

"Quake?" Sharan suggested, somewhat hopefully, and then screamed as the lab bounced energetically around them again. Lighting and acoustic panels fell from the ceiling; both Cainen and Sharan struggled to crawl under workbenches. The world imploded around them for a while as they cowered under their tables.

Presently the shaking stopped. Cainen looked around in what flickering light still remained and saw the majority of his lab on the floor, including much of the ceiling and part of the walls. Usually the lab was filled with workers and Cainen's other assistants, but he and Sharan had come in late to finish up some sequencing. Most of his staff had been in the base barracks, probably asleep. Well, they were awake now.

A high, keening noise echoed down the hall leading to the lab.

"Do you hear that?" Sharan asked.

Cainen gave an affirmative head dip. "It's the siren for battle stations."

"We're under attack?" Sharan asked. "I thought this base was shielded."

"It is," Cainen said. "Or was. Supposed to be, anyway."

"Well, a fine job, I must say," Sharan said.

Now Cainen was irritated. "Nothing is perfect, Sharan," he said.

"Sorry," Sharan said, keying in on her boss's sudden irritation. Cainen grunted and then slid out from underneath his workbench and picked his way to a toppled-over storage locker. "Come help me with this," he said to Sharan. Between them they maneuvered the locker to where Cainen could shove open the locker door. Inside was a small projectile gun and a cartridge of projectiles.

"Where did you get this?" Sharan asked.

"This is a military base, Sharan," Cainen said. "They have weapons. I have two of these. One is here and one is back in the barracks. I thought they might be useful if something like this happened."

"We're not military," Sharan said.

"And I'm sure that will make a huge difference to whoever is attacking the base," Cainen said, and offered the gun to Sharan. "Take this."

"Don't give that to me," Sharan said. "I've never used one. You take it."

"Are you sure?" Cainen asked.

"I'm sure," Sharan said. "I'd just end up shooting myself in the leg."

"All right," Cainen said. He mounted the ammunition cartridge into the gun and slipped the gun into a coat pocket. "We should head to our barracks. Our people are there. If anything happens, we should be with them." Sharan mutely gave her assent. Her usual sarcastic persona was now entirely stripped away; she looked drained and frightened. Cainen gave her a quick squeeze.

"Come on, Sharan," he said. "We'll be all right. Let's just try to get to the barracks."

The two had begun to weave through the rubble in the hall when they heard the sublevel stairwell door slide open. Cainen peered through the dust and low light to make out two large forms coming through the door. Cainen began to backtrack toward the lab; Sharan, who had the same thought rather faster than her boss, had already made it to the lab doorway. The only other way off the floor was the elevator, which lay past the stairwell. They were trapped. Cainen patted his coat pocket as he retreated; he didn't have all that much more experience with a gun than Sharan and was not at all confident that he'd be able to hit even one target at a distance, much less two, each presumably a trained soldier.