Ben and Linda nodded. Khalid merely stared.

"I say we go forward," Ashley said. "Any objections?"

The others remained silent.

"Fine," she said. "I want to be across that river in thirty minutes."

Ashley paced the river's edge. Villanueva had stripped to his underwear and cautiously waded into the oil-black water. A rope tied around his waist draped back to the team at the river's edge. Michaelson had anchored the rope around a stalagmite nearby.

"We could've all swum across by now," Ashley said. "All this jury-rigging is just wasting time."

"No," Michaelson said, looping a knot in the rope. "The current's too strong. If we tried to swim, someone could easily be swept away."

"Then just tie everyone together with rope." She didn't understand why he was being so obstinate. Didn't he realize every wasted second could mean Halloway's death?

Ben shook his head and tried to calm her with a smile. "Too easy to get tangled up, my dear. A good way to get someone drowned."

A loud splash drew her attention back to the river as Villanueva dove beneath the churning water, clearing half the stream before resurfacing. Strong arms cut the water in broad strokes, but still the current propelled the SEAL far downstream.

Linda grabbed Ashley's arm, pinching hard in panic. "Look!"

Ashley followed the biologist's outstretched arm back upstream from where they stood. A three-foot-tall dorsal fin, albino-white, crested the churning waters, then sank back from view.

Ben, openmouthed, had spotted it too. "Jesus Almighty Christ!"

Michaelson, with one hand tangled in the SEAL's anchoring rope, struggled to free himself, but the rope was cinched tight around his midsection. He freed his rifle and tossed it to Ben, who had the easier shot. "Use it. Before the thing reaches Villanueva."

Fumbling the rifle to his shoulder, Ben searched the water for his target. Then just below them a tip of white broke the surface, and a blast of rifle fire exploded. A small geyser of water erupted where the slug hit the water-a good several feet from the fin. Ben had missed.

"Shit," said Ben, pumping a second shell. Another miss.

Villanueva, having heard the shots over the noise of the river, had stopped and twisted around to stare at them, treading water. Linda and Ashley waved him toward the far shore. "Go! Get the hell out of there!" Ashley screamed.

The dorsal fin emerged again to its entire yard of height, now slicing the water halfway between the team and the SEAL In an arcing dive the SEAL flung his body toward the far shore, the water churned white by his pumping arms and legs. But the current resisted his progress; he seemed to be wallowing, like a fly in amber. He won't make it to shore, Ashley thought, clenching her fists, willing him strength.

The fin turned smoothly toward the thrashing SEAL.

Ben had raised the gun once more, then lowered it. "Damn it. I don't have a clear shot. At this angle, if I miss I could hit Villanueva."

Ashley snatched the rifle and raised it to her shoulder. Her first shot tore a chunk out of the fin. She aimed lower for the second shot, below the fin. As she pulled the trigger, the recoil crashed into her shoulder. This time the geyser of water from the shell's impact spurted red.

The fin tilted to the side, then sank from view.

Ashley's teeth ground together; she expected the injured creature to suddenly lurch out of the water and grind up the SEAL. She watched, the rifle butt pressed tight to her shoulder, as Villanueva reached the riverbank and scrambled up the slippery rock. He acknowledged the team's cheers with a wave and marched back upstream.

Ben stepped next to her, taking the rifle from her shaking hands. "I thought you hated guns."

She rubbed at her hands. "You've got to know something to hate it."

Ben just nodded, seeming to sense she didn't want to continue this conversation.

She stared across the river. Villanueva had untied the rope from his waist and was rigging his end to a thick stalagmite. Michaelson tugged the slack up and secured his end of the rope to a rock on this side, creating a rope bridge slung between two stalagmites. The two worked as if nothing had happened. As if some creature of nightmare hadn't just tried to swallow up one of their teammates.

The major tested the security of the bridge by tugging at it. Satisfied, he turned to the team. "Now we can cross."

Taking a deep breath, Ashley steadied her still-pounding heart. Put it behind you, she told herself. There is still a team to lead and a teammate to find.

Using carabiner hooks to attach waist harnesses to the rope, the team scooted hand over hand across the bridge. Dangling from the rope, Ashley was careful not to look down. The drop was not far, but the thought of what else might be lurking under the black reflection of water was paralyzing.

Villanueva, now suited back into his coveralls, helped her unhook from the bridge. His hand shook a bit as he helped her stand. Whether from the cold of the water or from the aftershock of such a narrow escape, she couldn't tell.

"Thanks," he said quickly, an embarrassed look in his eyes. "I owe you."

She tried to answer, but he turned his back to her and returned his attention to Michaelson, the last in line, as he crossed over the river.

As soon as the major had set his boots on the rocky edge, Ashley called everyone together. "This section of the cavern is much smaller, so we'll explore this area as a group. Let's head out. Keep your eyes and ears open. Whatever caused those screams may still be out there."

This search is futile, Khalid thought. He dug black mud from under a fingernail with a small blade. Halloway had to be dead. When would these damned idiots realize it so they could move on?

He watched the SEAL examine the wormhole they had discovered. No trace of the missing teammate had been found. They had searched behind every pebble and down every black crack. Nothing.

"This is no use," Villanueva said as he shined his flashlight down the wormhole. "No one's been through this hole in years. Look at the layer of mud at the entrance. No footprints or sled marks."

Ashley crouched at his side and pushed a finger knuckle-deep into the mud. "You're right. If anyone had passed, there would be some sign." She pushed back up and faced the team. "There's got to be another exit we missed."

"Maybe," Khalid said, trying to wake the team up, to get them redirected to the mission at hand. He had an agenda to follow, whether Halloway was found or not. "Maybe he got caught in the river and was washed away."

Michaelson shook his head. "No. The scream was well beyond the river's edge. I agree with Ashley. There must be another exit."

Khalid hid a scowl.

"Before we leave here," Ashley said, "I think we should send someone down this wormhole. Just to make sure. Any volunteers?"

Villanueva pulled out his sled. "I'll go."

She nodded. "Be careful. Just check out where this exits and come right back. No solo venturing."

He nodded and slipped into the hole. Ashley checked her watch.

Rolling his eyes at another delay, Khalid walked over to where Linda sat on a rock. She had her arms wrapped tight around her chest as he sat down beside her.

"Do you think we'll find him?" she asked, her voice tiny.

"No. No matter what the major believes, I think he was washed away."

Linda shuddered. He could tell what she was thinking. The fin had been as white as the belly of a maggot. Like some ghost shark coming to claim their souls. Men and rock he could handle, but the creatures down here… first the squid trying to gnaw his arm off and now this monster… The sight of that fin had made his flesh crawl. As if Nature were showing them how small they were.

He remembered, as a boy, hearing about the sandstorm that had buried his mother's camp in Syria, killing everyone. The black hand of Allah, they had called it, but he knew better. It was just Nature, an indifferent god, oblivious to the plans of man. To her savagery, everyone was vulnerable. And Khalid hated feeling vulnerable.

Linda hugged herself and kept staring back at the river. "That albino shark. It was huge. To support such a predator, the aquatic ecosystem down here must be more extensive than anyone had imagined. If it weren't for Halloway, I wouldn't mind stopping and doing some tests."

Khalid scowled, rubbing at his arm where the ammonite had bit him. "I'd rather avoid that ecosystem myself and stick to dry land."

"I found something!" Ben called from several yards away.

Khalid craned his neck to stare over at Ben. He stood by the cavern wall with a match in his hand.

Ashley called to him. "What is it, Ben?"

"I found another passage out of here."

Who was he kidding? Ashley thought, eyeing the narrow crack, buried in the shadowed fold of the rock face? It extended from floor to ceiling, but gapped only a foot wide. Easy to miss. "Nobody could fit through there," she said. "It's too narrow."

"No, I measured it," Ben said.

"With what?"

"My boot."

She gave him a blank stare.

"It's a caver's rule of thumb. 'If it's wider than your boot, through there one can scoot.'"

"I don't think so. Especially Halloway. He's a big guy."

"It would be a tight squeeze, but I know he could've fit."

"Besides, who knows if there's anything on the other side?"

In answer, Ben held up a lighted match to the crack. The flame bent away from the opening. "Wind," he said. "There's a breeze blowing from beyond there."

Ashley watched the flame flicker. Perhaps…

A scraping from the wormhole behind her drew her attention away. A pair of legs slid backward out of the opening. It was Villanueva. He stood up, wiping his hands on his knees.

"It's blocked," he said, huffing a bit. "There's a rock-fall blocking the passage about thirty yards in. I had a hell of a time backing all the way up here."