"Damn," I said, but then it was time to duck away, and shield my eyes from the explosive flash. Inside the confined space, there was a roar of expanding gas. I felt a burst of intense heat on my back. When I looked again, most of the swarms beneath us had vanished. But a few hung back, apparently undamaged.
They were learning.
Fast.
"Next lesson," Mae said, holding two caps this time. I lit both and she rolled one, and threw the second one deeper down the ramp. The explosions roared simultaneously, and a huge gust of hot air rolled upward past us. My shirt caught fire. Mae pounded it out with the flat of her hand, smacking me with rapid strokes.
When we looked again, there were no figures in sight, and no dark swarms.
We went down the ramp, heading deeper into the cave.
We had started with twenty thermite caps. We had sixteen left, and we had gone only a short distance down the ramp toward the large room at the bottom. Mae moved quickly now-I had to hurry to catch up with her-but her instincts were good. The few swarms that materialized before us all quickly backed away at our approach.
We were herding them into the lower room.
Mae said, "Bobby, where are you?"
The headset crackled. "-trying-get-"
"Bobby, come on, damn it."
But all the while we were moving deeper into the cave, and soon we heard only static. Down here, dust hung suspended in the air, diffusing the infrared beams. We could see clearly the walls and ground directly ahead of us, but beyond that, there was total blackness. The sense of darkness and isolation was frightening. I couldn't tell what was on either side of me unless I turned my head, sweeping my beam back and forth. I began to smell that rotten odor again, sharp and nauseating.
We were coming to level ground. Mae stayed calm; when a half-dozen swarms buzzed before us, she held out another cap for me to light. Before I could light the fuse, the swarms backed off. She advanced at once.
"Sort of like lion taming," she said.
"So far," I said.
I didn't know how long we could keep this up. The cave was large, much larger than I had imagined. Sixteen caps didn't seem like enough to get us through it. I wondered if Mae was worried, too. She didn't seem to be. But probably she wouldn't show it. Something was crunching underfoot. I looked down and saw the floor was carpeted with thousands of tiny, delicate yellow bones. Like bird bones. Except these were the bones of bats. Mae was right: they'd all been eaten.
In the upper corner of my night-vision image, a red light began to blink. It was some kind of warning, probably the battery. "Mae…" I began. Then the red light went out, as abruptly as it had begun.
"What?" she said. "What is it?"
"Never mind."
And then at last we came to the large central chamber-except there was no central chamber, at least, not anymore. Now the huge space was filled from floor to ceiling with an array of dark spheres, about two feet in diameter, and bristling with spiky protrusions. They looked like enormous sea urchins. They were stacked in large clusters. The arrangement was orderly. Mae said, "Is this what I think it is?" Her voice was calm, detached. Almost scholarly. "Yeah, I think so," I said. Unless I was wrong, these spiked clusters were an organic version of the fabrication plant that Xymos had built on the surface. "This is how they reproduce." I moved forward.
"I don't know if we should go in…" she said.
"We have to, Mae. Look at it: it's ordered."
"You think there's a center?"
"Maybe." And if there was, I wanted to drop thermite on it. I continued onward. Moving among the clusters was an eerie sensation. Thick mucuslike liquid dripped from the tips of the spikes. And the spheres seemed to be coated with a kind of thick gel that quivered, making the whole cluster seem to be moving, alive. I paused to look more closely. Then I saw that the surface of the spheres really was alive; crawling within the gel were masses of twisting black worms. "Jesus…"
"They were here before," she said calmly.
"What?"
"The worms. They were living in the layer of guano on the cave floor, when I came here before. They eat organic material and excrete high-content phosphorus compounds."
"And now they're involved in swarm synthesis," I said. "That didn't take long, just a few days. Coevolution in action. The spheres probably provide food, and collect their excretions in some way."
"Or collect them," Mae said dryly.
"Yeah. Maybe." It wasn't inconceivable. Ants raised aphids the way we raised cows. Other insects grew fungus in gardens for food.
We moved deeper into the room. The swarms swirled on all sides of us, but they kept their distance. Probably another unprecedented event, I thought: intruders in the nest. They hadn't decided what to do. I moved carefully; the floor was now increasingly slippery in spots. There was a kind of thick muck on the ground. In a few places it glowed streaky green. The streaks seemed to go inward, toward the center. I had the sense that the floor sloped gently downward. "How much farther?" Mae said. She still sounded calm, but I didn't think she was. I wasn't either; when I looked back I could no longer see the entrance to the chamber, hidden behind the clusters.
And then suddenly we reached the center of the room, because the clusters ended in an open space, and directly ahead I saw what looked like a miniature version of the mound outside. It was a mound about four feet high, perfectly circular, with flat vanes extending outward on all sides. It too was streaked with green. Pale smoke was coming off the vanes. We moved closer.
"It's hot," she said. And it was. The heat was intense; that's why it was smoking. She said, "What do you think is in there?"
I looked at the floor. I could see now that the streaks of green were running from the clusters down to this central mound. I said, "Assemblers." The spiky urchins generated raw organic material. It flowed to the center, where the assemblers churned out the final molecules. This is where the final assembly occurred.
"Then this is the heart," Mae said.
"Yeah. You could say."
The swarms were all around us, hanging back by the clusters. Apparently, they wouldn't come into the center. But they were everywhere around us, waiting for us. "How many you want?" she said quietly, taking the thermite from her pack.
I looked around at all the swarms.
"Five here," I said. "We'll need the rest to get out."
"We can't light five at once…"
"It's all right." I held out my hand. "Give them to me."
"But, Jack…"
"Come on, Mae."
She gave me five capsules. I moved closer and tossed them, unlit, into the central mound. The surrounding swarms buzzed, but still did not approach us.
"Okay," she said. She understood immediately what I was doing. She was already taking out more capsules.
"Now four," I said, looking back at the swarms. They were restless, moving back and forth. I didn't know how long they would stay there. "Three for you, one for me. You do the swarms."
"Right…" She gave me one capsule. I lit the others for her. She threw them back in the direction we had come. The swarms danced away.
She counted: "Three… two… one… now!"
We crouched, ducked away from the harsh blast of light. I heard a cracking sound; when I looked again, some of the clusters were breaking up, falling apart. Spikes were rolling on the ground. Without hesitating, I lit the next capsule, and as it spit white sparks, I tossed it into the central mound.
"Let's go!"
We ran for the entrance. The clusters were crumbling in front of us. Mae leapt easily over the falling spikes, and kept going. I followed her, counting in my mind… three… two… one…
Now.
There was a kind of high-pitched shriek, and then a terrific blast of hot gas, a booming detonation and stabbing pain in my ears. The shock wave knocked me flat on the ground, sent me skidding forward in the sludge. I felt the spikes sticking in my skin all over my body. My goggles were knocked away, and I was surrounded by blackness. Blackness. I could see nothing at all. I wiped the sludge from my face. I tried to get to my feet, slipped and fell. "Mae," I said. "Mae…"