He redirected his light toward the ceiling, forty feet above. Different formations loomed there: huge stalactites hanging in clumps, great daggers of stone pointed toward them, some of them fifteen feet long, three feet thick at the base. Cutting between them was an angled row of smaller, jagged spikes, like an endless row of shark’s teeth, a formation known as a welt line, and farther off an array of delicate strands called soda straws dangled from an overhang, their tips glistening with moisture.

“Hell of a cave,” he said. The words echoed.

Behind him McCarter, Danielle and Verhoven were reaching the same conclusion. “Sulfur cave,” McCarter said, shining his own flashlight around. “Most caves are formed from limestone, but some are carved from the rock by the effects of sulfuric acid. Lechugila in New Mexico for instance. That might explain the acidic water in the bottom of the well. This water too.”

Hawker scanned the water with his light. He and Verhoven had viewed Lang’s recording several times and they’d heard large splashes. They knew the danger came from the water, but the immediate area seemed to be clear.

“Which way?” Danielle asked.

Hawker pointed. “There’s a pathway on the right; it leads to the other side.”

He clipped his flashlight to the barrel of his rifle. The others followed suit, except for Verhoven, who carried a different weapon—a pump-action Mossberg shotgun lifted from Kaufman’s arsenal. His right hand held the trigger, his swollen left hand duct-taped to the pump, tight enough that he could reload it.

They moved onto the pathway, traveling in a single file and watching the water for any sign of danger. Hawker had the point, with Danielle right behind him. She wore a small backpack stuffed with equipment while a portable Geiger counter strapped to her leg clicked away softly.

“Just a precaution,” she’d explained. “The Martin crystals showed traces of radioactive contamination. So does the soil up above.”

“Thanks for telling us.”

“Don’t worry,” she said. “It’s all low level. We’d have to stay here for years to be affected.”

If there was one thing Hawker was sure of it was that they wouldn’t be sticking around that long. He continued on, following the rugged pathway to the dam. The seven pools and the smooth stone of the plaza lay just beyond.

Hawker stopped. “The last images on the recording were of this place. You ready?” he asked Verhoven.

Verhoven nodded. “You know those shells won’t do much beyond a depth of five or six feet.”

“Yeah,” Hawker replied. “But it’ll be a hell of a wake-up call if anything’s down there.”

Verhoven nodded. “I’ll watch your back.”

Hawker moved away, stepping onto the dam, scanning the lake and then turning his back to it. Verhoven took a position at the end of the structure, poised and ready should something come at Hawker from the lake behind.

Hawker stepped up to the first pool, fired two quick bursts into it and then jumped back, waiting for some reaction.

The sound of the gunfire boomed through the cave and echoed back at them from the darkness, vibrating in receding, diminishing waves, but nothing moved in the pool. One down, six to go.

Hawker stepped toward the other pools and repeated the procedure until the entire honeycomb arrangement was clear. It appeared that the pools were empty.

He stepped off the dam and made a quick inspection of the surrounding area. Satisfied, he gave the all-clear.

“Strange formation,” McCarter said. “Seven pools. I wonder: Seven Caves, Seven Canyons.”

Danielle acknowledged him. “And the Place of Bitter Water,” she said.

Hawker aimed his flashlight across the plaza and into the cave beyond. Fronted by the lake, the plaza stretched sideways for at least a hundred feet, with the back edge hard against the cave’s stone wall. On the side closest to them lay the dam and the pools and more open cave. On the far side, the broken trail of the pathway seemed to continue into a deeper section of the cavern. Hawker guessed that would be the way to go.

He brought the beam of his light back across the plaza, toward the path they’d just come down. He stopped. Ripples were moving slowly across the surface of the lake, a surface that had been like glass only moments before. His eyes darted back and forth, as he swung the beam of light through the depths of the cave and back out over the water once again.

“What’s wrong?” Danielle asked.

“Something disturbed the water,” he said. “Went in or came out.”

The dried swaths of blood on the stone showed that both victims had been killed in the open part of the plaza. Not a good place to stand. “Come on,” he said. “We need cover.”

Hawker led them to the back of the plaza, to a spot where the smooth floor butted up against the jagged natural stone of the wall. They pressed themselves against it, with Hawker on the right end and Verhoven on the left and the broad open space of the plaza in front of them. It was a good spot tactically, nothing could come at them from behind, only from the sides and front, and that would leave any attacker open to a withering fire.

“You see anything?” Verhoven asked.

“Just the water.”

Verhoven went to speak again but stopped as muted noise reached their ears, a scraping sound, a raspy scratching, like stone dragged across stone.

Danielle switched off the Geiger counter so they could listen.

“What was that?” McCarter whispered.

No one could say. But their eyes darted around in search of its source, their lights crisscrossing in the dark.

The sound returned. Two long, slow scrapes, preceded by a strangely muted click.

The group fell into utter silence, barely breathing, their eyes straining into the dark.

“What if it’s Susan?” McCarter asked. They had tried to reach her on the radio several times since entering the cave, but to no avail. “What if there was a cave-in and she’s trapped and trying to signal us? Avalanche victims are found like that sometimes.”

Hawker listened as the sounds were heard once again. “It’s not her,” he said.

“Are you sure?” McCarter asked. “It could—”

“The sounds are overlapping,” Hawker said. “There’s more than one source.”

From out of the darkness the scraping noise whispered to them, soft but unmistakable now: click, click, scrape, scrape.

“Where the hell is it coming from?” Danielle asked, her eyes darting back and forth.

It was a fair question. With the strange acoustics of the cave, the noise seemed to be coming from everywhere at once. Click, click … scrape, scrape, click, click.

To Hawker’s left, Danielle and McCarter struggled to keep still. He ignored them, grimly sweeping his field of view. He knew Verhoven would be doing the same, and that, armed and waiting with their backs pressed to the wall, they were in a good position. Whatever was out there, stalking them, crawling from the edge of the lake or moving toward them from the farther depths of the cave, it would have to cross the open ground before it could strike.

“Stay against the wall,” he whispered. “Whatever happens, stay back against the wall and out of our way.”

Click, click, scrape, scrape. Louder this time, closer.

Danielle and McCarter pressed into the stone.

Hawker squinted into the darkness, waving the light around. To the right side—his side—the plaza ran for sixty feet before the jagged teeth of the cave took over once again. Beyond that, the cave opened up and a long finger of the lake appeared to stretch into the rocky formations beyond. That area offered the only real cover for anything approaching them, but a near-constant watch had caught nothing. “On your side, Pik.”

Verhoven shook his head. “I don’t think so.”

Click, click.

“Has to be.”

Verhoven bristled. “I’m telling you, there’s nothing over here.”