Sullivan went first, favoring his bad leg. Then Guilford, favoring his own. The frontiersman followed behind. The down-spiraling walkway was broad enough that Guilford was able to avoid looking directly into the well’s smoky deeps.

He couldn’t guess what this well had been made for or who might have walked this way in ages past. Nor how far down it might descend, into what lava-heated cavern or glowing underworld. Hadn’t the Aztecs used wells for human sacrifice? Certainly nothing much good could have happened down this rabbit hole.

Sullivan called a halt when they had descended, by Guilford’s estimate, a hundred feet or more. The rim of the well was as invisible now as the bottom, both hidden in lofting spirals of fog. Sullivan was winded and gasping, but his eyes were bright in the strange, dim radiance.

Guilford wondered aloud whether they hadn’t come far enough. “No offense, Dr. Sullivan, but what exactly do you expect to find here?

“The answer to a hundred questions.”

“It’s some kind of well or cistern,” Guilford said.

“Open your eyes, for God’s sake! A well is what this is not. If anything, it was designed to keep groundwater out. Do you think these stones grew here? The blocks are cut and the joints are caulked… I don’t know what the caulking material is, but it’s remarkably well preserved. In any case, we’re already below the water table. This is not a well, Mr. Law.”

“Then what is it?”

“Whatever its purpose — practical or ceremonial — it must have been important. The dome is a landmark, and I’d guess this passageway was meant to accommodate a great deal of traffic.”

“Traffic?”

“The city builders.”

“But they’re extinct,” Guilford said.

“You hope,” the frontiersman muttered from behind.

But there was no end to the descent, only this spiral of stone winding monotonously into blue-tinted fog, until even Sullivan admitted he was too fatigued to go any farther.

“We need,” he said at length, “more men.”

Guilford wondered who he had in mind. Keck? Robertson? One-armed Digby?

Tom looked up the way they had come, now a colorless overcast. “We shouldn’t wait to turn back. Daylight’ll be gone soon — what there is of it.” He cast a critical eye at Sullivan. “When you get your breath back—”

“Don’t worry about me. Go on! Reverse order. I’ll follow behind.”

He was pale and dewed with sweat.

The frontiersman shrugged and turned. Guilford followed Tom, calling a halt whenever the line between himself and Sullivan grew taut. Which it often did. The botanist’s breathing was audible over a considerable distance now and it grew more labored as they climbed. Before long Sullivan began to cough. Tom looked back sharply and slowed the ascent to a crawl.

The fog had begun to thicken. Guilford lost sight of the far wall, stone steps vanishing behind a twining curtain of vapor. The rope served a purpose now, as even Tom Compton’s broad back grew faint in the mist.

With the loss of visible landmarks came disorientation. He couldn’t guess how far they had come or how much of the climb remained. Doesn’t matter, he told himself sternly. Every step is one step closer. His bad leg had began to hurt him, a vicious pain that ran like a wire from calf to knee.

Shouldn’t have gone so far down, Guilford thought, but Sullivan’s enthusiasm had been contagious, the sense of some immense revelation waiting, if only they could reach it. He stood a moment, closed his eyes, felt chill air flow past him like a river. He smelled the mineral smells of granite and fog. And something else. Muskier, stranger.

“Guilford!”

Tom’s voice. Guilford looked up sheepishly.

“Watch where you’re standing,” the frontiersman said.

It was the brink of the escarpment. Another step and he might have fallen.

“Keep your left hand on the wall. You too, Sullivan.”

Sullivan came into view, nodding wordlessly. He was a shade, a wraith, a gangly spirit.

Guilford was groping his way behind the frontiersman when the rope suddenly cinched at his waist. He called a halt and turned.

“Dr. Sullivan?”

No answer. The rope remained taut. When he looked back he saw only fog.

“Dr. Sullivan — are you all right?”

No answer, only this anchoring weight.

Tom Compton came scrabbling out of the mist. Guilford backed up, slacking the rope, peering into the dimness for any sign of Sullivan.

He found the botanist lying on the wide granite ledge, face down, one hand still touching the damp rock wall.

“Ah, Christ!” Tom dropped to his knees. He turned Sullivan over and searched his wrist for a pulse.

“He’s breathing,” the frontiersman said. “More or less.”

“What’s wrong with him?”

“Don’t know. His skin’s cold and he’s ungodly pale. Sullivan! Wake up, you son of a bitch! Work to do!”

Sullivan didn’t wake up. His head lolled to one side, limply. A trickle of blood escaped one nostril. He looks shrunken, Guilford thought dazedly. Like someone let the air out of him.

Tom stripped his pack and bunched it under the botanist’s head. “Stubborn fucker, wouldn’t slow down for love of life…”

“What do we do now?”

“Let me think.”

Despite their best efforts, Sullivan wouldn’t wake up.

Tom Compton rocked on his heels for a time, deep in thought. Then he hitched his pack over his shoulder and shrugged out of the rope harness. “Hell with it. Look, I’ll bring blankets and food from the sledge for both of you. After that you stay with him; I’ll go for help.”

“He’s wet and nearly freezing, Tom.”

“He’ll freeze faster in the open air. Might kill him to move him. Give me a day to reach camp, another day to get here with Keck and Farr. Farr will know what to do. You’ll be all right — I don’t know about Sullivan, poor bastard.” He frowned fiercely. “But you stay with him, Guilford. Don’t leave him alone.”

He might not wake up, Guilford thought. He might die. And then I’ll be alone, in this godforsaken hole in the ground.

“I’ll stay.”

The frontiersman nodded curtly. “If he dies, wait for me. We’re close enough to the top, you ought to be able to tell night from day. You understand? Keep your fucking wits about you.”

Guilford nodded.

“All right.” Tom bent over the unconscious shape of Sullivan with a tenderness Guilford had never seen in him, smoothed a strand of gray hair from the botanist’s dank forehead. “Hang on, you old cock-knocker! You damn stupid explorer.”

Guilford took the blankets Tom brought him and made a rough bed to shield Sullivan from cold air and cold stone. Compared to the atmosphere outside the temperature in the well was nearly balmy — above the freezing point; but the fog cut through clothing and chilled the skin.

When Tom vanished into the mist Guilford felt profoundly alone. No company now but his thoughts and Sullivan’s slow, labored breathing. He felt both bored and near panic. He found himself wishing stupidly for something to read. The only reading matter that had survived the Partisan attack was Digby’s pocket New Testament, and Diggs wouldn’t allow it out of his possession. Diggs thought the onion-leafed book had saved his life: it was his lucky charm. Argosy was long lost.

As if a person could read, in this arsenic-colored dusk.

He knew night had fallen when the light above him faded entirely and the moist air turned a deeper and more poisonous shade of green. Minute particles of dust and ice wafted out of the deeps, like diatoms in an ocean current. He rearranged the blankets around Dr. Sullivan, whose breathing had grown harsh as the rasp of a saw blade in wet pine, and ignited one of the two mosquewood torches Tom Compton had brought him. Without a blanket of his own, Guilford shivered uncontrollably. He stood up whenever his feet grew numb, careful to keep one hand on the rock wall. He propped the torch in a cairn of loose rocks and warmed his hands at the low flame. Mosquewood dipped in snake tallow, it would burn for six or eight hours, though not brightly.