Waiters served them another round of hors d'oeuvres: ammonite escargot.

"There was a time when they ruled the seas, reaching ten feet across," Geoffrey said. "The Roman historian, Pliny the Elder, named them after examining their fossils near Pompeii and noted their resemblance to the ram horns worn by the Egyptian god Amon. You know, the one King Tut was named after? But this is impossible...."

"Amen," said Otto.

"Don't laugh," Nell said. "But we probably adopted that word from the tradition of invoking Amon in prayers."

Maxim laughed. "Go on."

"Some think these creatures may have plowed across the sea's surface like Jet Skis, hunting with heads and arms like armored squid," Geoffrey said.

"Well, they were right, Geoffrey," Maxim said. "I've seen them do it."

"Do you know how huge a discovery this is?" Katsuyuki said, his hands shaking. "It's a miracle!" Otto gave him a high five.

"How do they taste?" Maxim asked.

"We're eating them?" Nell asked.

"Oishii!" Katsuyuki nodded, elated. "Delicious."

"Chewy," Otto said, laughing.

"And that's a sea spider," Geoffrey said, pointing at the multicolored eight-legged creature that reached its impossibly long, folding arms out to the racing ammonites. "One of the strangest crustaceans. This one's really colorful! They seem to be a branch that split off from all other arthropods about half a billion years ago..."

"Some think they actually are arachnids-before they evolved for land," Otto said.

"That's debatable, Doctor," said Katsuyuki, admiring the specimen.

"It's still a cool theory," Otto said. "What's in this one?"

An attendant pulled the shroud from the next tank, which was dry. Inside, yellow and orange animals that glowed circled round and round on the bottom.

"Gammarids?" Geoffrey suggested, looking into the dry aquarium.

"Yes," agreed Dimitri. "Some kind of amphipod, like gammarids, we think. We call them gammies."

"But adapted for land?" Geoffrey said. "With only eight legs?"

"Look at the spikes on their backs," Nell said. "They look like aetosaurs!"

"What are aetosaurs, Nell?" Maxim asked, leaning back in his chair and watching the scientists as waiters served another round of appetizers and replenished their champagne.

"One of my favorite dinosaurs, with spikes on its back pointing to each side."

"It's thought that gammarids may have evolved in Lake Baikal or the Caspian Sea, which isn't so far from here, I think," Otto said.

Dimitri smiled. "Lake Baikal is rather far from here, Dr. Inman. But you are right, the gammarids there have similar spikes on their armor."

"They're also known as killer shrimp," said Otto. "They're a big concern at Berlin University. They've been migrating from the Caspian Sea across Europe through the Danube and wreaking havoc. They've even been turning up in England and Scotland recently. But no one has ever recorded a land-based species! And with only four pairs of legs?"

"They must have undergone an independent Hox gene mutation, like early arthropods, when they crawled on land four hundred million years ago and became hexapods," Geoffrey said.

"Hexapods?" Maxim asked.

"Bugs," Geoffrey clarified. "With only six legs."

"But why are they glowing?" Nell wondered. "They seem to be blind. No eyes, at all! See?"

"They move like tiger beetles!" Katsuyuki exclaimed with an eight-year-old's delight. "So fast! But why in a circle, around and around?"

"We've noticed they move like that sometimes," Dimitri acknowledged, shrugging.

"Wait a minute ... army ants," Nell murmured.

"Huh?" the others asked.

"Army ants are blind, so they follow scent trails laid down by other ants' abdominal glands. If an ant travels in a spiral, others following it can get trapped in death circles, with thousands of them turning like hurricanes until they die of starvation."

"No way," Otto said. "I've never heard of that."

"But why do the gammies glow if they're blind? Why do any of these species? I don't get it."

"They eat ... what did you call it? Rainbowfire," Maxim said.

"We think the bioluminescence in the fungus either grows on them or continues to glow once ingested," Dimitri said.

"They must stick out like Christmas lights to predators," Nell said, puzzling. "Maybe that's why they're covered with spikes...."

"How long would adaptations like these take to evolve?" asked Katsuyuki, shaking his head.

"Well, Lake Baikal is the oldest freshwater lake on Earth." Dimitri shrugged. "It lies hundreds of kilometers east of the Urals."

"How old is it?" asked Nell.

"Some say fifty million years."

"It might be a clue." Nell looked at Geoffrey.

"The Caspian Sea is a lot closer," Geoffrey said. "And the Aral Sea. And in any event, I don't think any of them are old enough. We're looking at things that must have origins dating back to the great age of marine mollusks, which ended around the time of the dinosaurs sixty-five million years ago. This is a region with major tectonic activity, which made these mountains. What I don't understand is how could a cave system this size last for so long?"

"The Urals are the oldest mountain range on Earth, Dr. Binswanger. They are two hundred fifty, maybe three hundred million years old," said Dimitri.

"Ah! Who knows when these specimens were trapped underground and begun diverging, then?" Otto said.

Nell whispered in Geoffrey's ear: "This is much better than Kauai, sweetheart."

He nodded and speared a gammarid tail, dipping it in cocktail sauce as she clinked her flute of champagne against his.

The attendant pulled the shroud from the third tank.

The German electrical engineer, Klaus Reiner, who had watched and listened in silent awe as the scientists described the species presented to them at this extraordinary banquet, now spoke up. "What in hell are these?" he said, pointing at glowing bubbles bobbing up and down inside the dry tank.

The others were silent.

Maxim laughed softly.

"We have no idea," Dimitri confessed, "what these are."

Small creatures like Christmas tree ornaments glowed pink and orange with four fins that made them spin or glide as they floated up and down.

"How are they doing that?" asked Otto.

"They look like Dumbo octopuses!" Nell said. "Are they filled with gas?"

A light like an ignited match flared inside one of the small bell-like creatures as it rose inside the tank.

"Bombardier beetles!" exclaimed the German.

The scientists turned to him.

"Sorry. I did a paper on them as an undergraduate...."

"I thought you were an electrical engineer," Nell said.

"I was studying biochemical energy systems for a while."

"Explain, please, Dr. Reiner," Maxim said.

"Bombardier beetles mix hydrogen peroxide and hydroquinone generated in separate glands to create an explosive chemical reaction, like a rocket engine. It generates enough heat to boil water. These things might be using a similar process to inflate a bladder with hot gas."

"Like sky lanterns," Katsuyuki said.

"Hot air balloons!" Nell said.

Maxim blew a plume of cigar smoke straight up. "Excellent."

Geoffrey shook his head, staggered by the implications. "We've got water, land, and air organisms? How elaborate is this ecosystem?"

"Let me show you." Maxim nodded at one of his men, and the man pulled a golden sash that parted the red velvet curtains at his back, revealing a great oval window encircled by a wide bronze frame embedded in the solid rock.

Everyone rushed to the window before the curtains had completely opened, and Maxim swiveled in his leather chair to gaze with them through the thick pane of glass that stretched twenty feet high and forty feet wide. The polished window was dark except for glowing colors and shapes that slowly began to emerge. "Ladies and gentlemen," Maxim said, "May I present Pandemonium."

9:55 P.M.

Slowly, their eyes made out the outlines of another world on the other side of the window.

A vast lake, splotched with swirling patches of color, channeled into the distance through a corridor angling slightly to the right as far as the eye could see. Hundreds of feet above was a vaulted ceiling with iridescent paisley patterns overlapping over the rock.

The faint light of the chandeliers lit up the area closest to the window. As suspended forms moved closer in the dark, they took on real shape; as they moved away, they dissolved into spectral ciphers. Multitudes of phosphorescent creatures swirled in glowing storms and spiral galaxies receding to the vanishing point in the colossal cavern.

Geoffrey scanned the surface of a lake below. He saw creatures snaking over the water, visibly breaking into pieces and rejoining as they swam like the centipede Maxim had shown them. Bioluminous hordes of gammarids darted over glowing patches on the lake's surface.

All the scientists were pressed against the window, cupping their hands to both sides of their heads as they peered through the thick glass. Nell looked up at the cavern's ceiling, which was coated with a shaggy pelt of stalactites. An island of stalagmites the size of buildings soared from the center of the lake with columns reaching all the way to the ceiling at its highest point, six hundred feet above. And every spire was dusted with rainbowfire.

Purple globes the size of beach balls dangled red tentacles like levitating Portuguese man-of-wars. A faintly illuminated organism like a Macy's Thanksgiving Day parade float moved languidly over the lake in the distance, extending long feathery plumes at one end that fanned cyclones of orange and pink bubbles into its whale-sized mouth.

Nell sighed, holding on to Geoffrey. "What in the hell are we looking at?"

Maxim pointed to a plaque centered on the bottom frame of the window.

"'Hell's Window,'" Maxim translated. "That's just what Stalin thought he was looking at as he sat in this very chair. I imagine he felt right at home. As for me, I call it Pandemonium." He spoke in Russian to one of his men to the right of the window, who nodded as he pulled down a heavy switch.

The chandeliers dimmed to a flicker, and a rack of locomotive headlamps mounted inside the cavern ignited above the window and flooded the chasm with beams of light. The patches on the lake's surface now appeared to be gray masses like shingled lily pads over which yellow and orange gammarids scrambled. Along the shore, more of the amphipods flowed in herds, ranging from the size of mice to hippos. More poured down over the window from above and across its lower ledge.

Overcoming their initial shock, the scientists began exclaiming all at once, each reacting to something else as they pointed in different directions.

One of the yellow and pink striped blimps drifted toward them under the spiked ceiling. Spiraling feathers recoiled one by one from the air as they snagged swarms of orange and pink balls like the specimens in the tank on the table before them.

"Fuck me!" Otto laughed, delirious as he hung on the window like a boy at the monkey enclosure.

"Sky whales," Nell breathed.

"Good!" Maxim approved.

"Could it be some kind of medusae or mollusk?" Geoffrey wondered, gripping Nell's hand. He realized, as did the rest of the scientists, that not only hundreds of millions of years but also a truly vast environment would be required to produce such a variety of life and all these complex interrelationships.

"The gammies are all over the ceiling, too!" Otto pointed up at the cavern's vault, which was overrun by amphipods grazing on the stalactites.

"Look at that nearest herd, crossing the lake," said Dimitri. "The ones at the perimeter have mandibles."

"Maybe it's another antlike adaptation," Nell said. "Some gammies might be specialized to defend the colony."

"Maybe they're predators, stalking the herd," Katsuyuki said.

"That layer on the lake looks like the bacteriafungus mats in the Movile cave in Romania," Nell said. "It grows chemosynthetically and is the base of the food chain for thirty-three endemic species."

"Interesting," Maxim said.

"Everything seems to eat the rainbowfire on the walls and ceiling, too," added Geoffrey.

"And everything glows," Katsuyuki said. "Maybe there is a connection!"

"I don't know," Nell said. "Digestive enzymes would pretty quickly denature the luciferase that makes the fungus glow...."

"Most things down here are probably transparent," Geoffrey said. "So their food would glow at least partway down even if the luciferase were hydrolyzed by digestive enzymes."

"Maybe," she considered. "Or maybe the organisms are simply coated by glowing spores."