Karla hesitated. Her first impulse had been to flee in the other direction. But Schroeder seemed to know what he was doing. She hurried to catch up.

The alley led to another street similarly lined with buildings. The street was deserted. There were only the squat little structures with their windows staring like vacant eyes in the strange half-light. Schroeder checked his internal compass, and again started in a direction he hoped would take them to the far side of the city.

After they had walked for a few blocks, Schroeder stopped suddenly and raised his rifle. He lowered the weapon after a second and rubbed his eyes. "This strange light has me crazy. Now it's my turn to start seeing things. I saw something run from one side of the street to the other."

"No. I saw it too," Karla said. "It was large. I don't think it was human."

Schroeder started off again. "That's good. We haven't had much luck with humans lately."

Karla's nostrils picked up a familiar musky odor. The shed housing the baby mammoth had the same smell. Schroeder's nostrils had picked up the scent as well.

"Smells like a barnyard," he said.

The fragrance of mud, animals and manure became stronger as they made their way through an alley to another street. The street ended in a plaza similar to the public square they had encountered at the entrance to the city. The plaza was rectangular, about two hundred feet to a side. Like the earlier square it was dominated by a step pyramid about fifty feet high. But what caught Karla's eye was the immediate area around the pyramid.

Unlike the first plaza, whose pavement was made of the same glowing stone as the rest of the city, this space looked as if it were covered by a thick dark growth of weeds or grass. Karla's first impression was that she was looking at an untended garden similar to something she might see in a public park. That didn't make sense given the lack of sunlight. Drawn by her natural curiosity, she started toward the pyramid.

The vegetation began to move.

Schroeder's aging vision had trouble seeing details in the half-light, but the movement caught his eye. The training ingrained long ago came into play. He'd been taught that the best insurance when faced with a potential threat was a lead curtain. He stepped in front of Karla, and he brought his rifle to his hip. His finger tightened on the trigger as he prepared to saturate the square with a lethal spray.

"No!" Karla shouted.

She put her hand in front of his chest.

The plaza undulated, and from the moving mass came a sound of snorts and squeaks and heavy bodies starting to stir. The image of vegetation disintegrated, to be replaced by large furry clumps the size of large pigs.

Schroeder stared at the strange creatures milling around the square. They had stubby trunks and upturned tusks, and their hides were covered with fur. The significance of what he was seeing finally dawned on him.

"Baby elephants!"

"No," Karla said, amazingly calm in spite of her unbounded excitement. "They're dwarf mammoths."

"That can't be. Mammoths are extinct."

"I know, but look closely." She pointed the flashlight at the animals. A few of them glanced at the light, showing shiny round eyes of an amber hue. "Elephants don't have fur like that."

"This is impossible," Schroeder said as if he were having a hard time convincing himself.

"Not entirely. Traces of dwarf mammoths were found on Wrangel Island as recently as 2000 B.C. That's only a blip in time. But you're right about this being unbelievable. The closest I've come to these creatures has been the fossilized bones of their ancestors."

Schroeder said, "Why don't they run away?"

The mammoths seemed to have been sleeping when they were disturbed by the human intruders, but they weren't alarmed. They moved around the square in singles, twosomes or small groups, and showed little or no curiosity at the strangers.

"They don't think we'll hurt them," Karla said. "They've probably never seen humans before. My guess is that they evolved from the full-grown animals that we saw in the murals. They've adjusted to the lack of sunlight and food through generations."

Schroeder gazed at the herd of pigmy mammoths and said, "Karla, how do they live?"

"There's an air supply. Maybe it seeps down from the ceiling, or through crevasses we don't know about. Maybe they've learned to hibernate to preserve food."

"Yes, yes, but what do they eat?"

She glanced around. "There must be a source somewhere. Maybe they get out into the open. Wait! Maybe that's what happened to the so-called baby that the expedition found. It was looking for food."

"We must try to find out where they go," Schroeder said. He made his way to the pyramid with Karla close behind. The mammoths moved aside to create a path. Some were slow to get out of the way and brushed against the humans, who had to wind their way through piles of manure. They reached the pyramid steps and began to climb. The effort put pressure on Schroeder's weak ankle, and he had to climb on his hands and knees, but he made it slowly to the flat top of the structure.

The elevation offered a total view of the square. The animals were still milling around with no rhyme nor reason to their movements.

Karla was counting the animals and figured there were about two hundred of them. Schroeder had been scanning the disorganized mob with other goals in mind, and, after a few minutes, he saw what he was looking for.

"Look," he said. "The mammoths are forming into a loose queue over there near that corner of the plaza."

Karla looked at where Schroeder was pointing. The herding animals had squeezed into a street as if suddenly inspired by a common purpose. Other mammoths began to follow, and soon the whole group was moving toward the same part of the square. With Karla helping him, Schroeder climbed off the pyramid and hobbled after the departing herd.

By the time they got to the corner, the entire herd had vanished from the square and was moving slowly along a narrow street that led back to the main boulevard. They tried not to startle the animals, although that didn't seem to be a danger. The mammoths seemed to have accepted the newcomers as part of the herd.

After about ten minutes, they began to see a change in the character of the city. Some of the houses on both sides were damaged. Their walls were knocked in as if hit by a rogue bulldozer. Eventually, they came to an area that looked as if it had been bombed. There were no freestanding buildings, only glowing piles of rubble intermingled with huge boulders made of a different, nonluminous mineral.

The sight revived unpleasant memories for Schroeder. He stopped to give his ankle a rest and looked around at the ruined landscape. "This reminds me of Berlin at the end of World War Two. Come. We must hurry or we'll lose them."

Karla dodged a pile of manure. "I don't think we'll have to worry about that with the trail they're leaving."

Schroeder's deep laughter echoed off the walls of rubble that now arose high on both sides. Karla joined in despite her weariness and fears, but they picked up the pace more in eagerness to find a way out than concern at losing the herd.

More of the rock they were seeing was composed of nonglowing material. Then all trace of the luminescent rock disappeared and the path in front of them darkened. Karla turned the flashlight on, and its dim beam caught the tails of the mammoths. The creatures had no trouble navigating the darkness. Karla guessed that their eyes must have adjusted to the lack of light in the same way their bodies had shrunk to accommodate a diminishing supply of food.