The sound was faint at first, a high-frequency whistling that grew steadily louder when she listened carefully.

She looked around at the blank stares of the people around her. They didn't understand. They didn't hear. Her voice was halting as she spoke.

"Look! My chip is picking up some kind of noise."

"What do you mean, noise?" Ivan looked around. "I don't hear a-"

As if in answer, the lens of his flashlight suddenly exploded and went out, too, in a shower of glass.

The corner of the cavern was darker now with two less lights. Sinjira's feeling of uneasiness was quickly shifting into genuine fear.

What the hell is going on here?

She jumped and let out a piercing squeal when Rodriguez's flashlight lens exploded.

And then Ruth's ... and finally Jordan's.

Sinjira felt panicked as she tried to understand whatever this was that her chip was picking up, and that could shatter their flashlights.

"Wait a second," Ivan said. "I think I can-"

He cupped his hands to his ears and turned his head back and forth as though trying to locate the origin of whatever the sound was.

"You hear it, too?" Sinjira asked.

Ivan waited, then nodded slowly.

"I think so. Just barely..."

"I don't hear anything," Rodriguez said. "You're probably just..."

His voice trailed off, and he scrunched up his face as he, too, listened.

Sinjira kept wheeling her head left and right, trying to pinpoint the source of the sound.

Right now it seemed to surround her.

Rising higher.

Turning even more shrill.

She licked her lips, aware of the dry, crusty texture. When she wiped the flat of her hand across her face, she felt something sticky.

She let out a faint groan when she saw the streak of blood on her palm.

No!

The sound was inside her head now. If it didn't stop soon, it would drive her crazy.

"We have to ... get out of here!" she shouted, surprised by the strength of her voice. "There's some kind of-"

"The sound's painful," Ivan said, shaking his head as if he had water in his ears. "Anyone else hear it?"

Sinjira watched as each of them looked hurt ... crippled by the noise.

Suddenly, Ruth doubled over and grabbed her head with both hands. Blood was streaming from both of her nostrils. It glistened darkly in the dim light.

Sinjira looked down at her chip. Still recording, but the levels were all wrong.

"This is going off the scale, way past any UHF. The noise isn't even close to normal frequencies."

First Ruth, then Rodriguez fell to their knees, clutching their heads. Ivan came up to Ruth, covering his ears.

"It's a trap," he said. "The sound..."

Like the mirrors with light, only now it was sound.

"We have to get away from it," Ruth said. Blood ran freely from her nose to the edge of her chin.

By now, everyone was blocking their ears with their hands, but Sinjira could feel the sound still swelling, building up pressure inside her brain.

Covering their ears would do nothing.

This sound could penetrate their skulls.

She looked at the trickle of blood leaking between Jordan's fingers as he covered his ears.

Ivan walked over and yanked Ruth and Rodriguez to their feet. He started dragging them away, back to the main room, forcing them to run.

Sinjira, with Jordan following, ran after them.

Their footsteps made harsh, hissing sounds in the dust as they ran, sprinting as fast as they could to put as much distance as possible between them and the origin of that high-frequency sound.

How far will we have to get away from it before it won't affect us?

Ivan ran as fast as he could, dragging Ruth and Rodriguez. Like them, he was nearly immobilized by the sound but kept pushing.

Behind them was Annie, Sinjira, and-finally-Jordan, perhaps bleeding the most, his ears shiny with red blood.

"Ingenious," Rodriguez said, gasping.

"What's that?" Ivan said, still pulling him along.

"A hypersonic defense system," Rodriguez went on. "If we had stayed there much longer, the sound-basically inaudible, like an old-fashioned dog whistle-would have ruptured our blood vessels, maybe even cracked our skulls, made our heads explode."

"Like what was on the wall," Sinjira said.

"Yeah. Fucking brilliant," Annie said, panting as she ran, her fists clenched and pumping like pistons.

"Can you still read it on your chip?" Ivan asked Sinjira.

She nodded and said, "It's fainter ... but still there."

Ivan thought: What if there was another trap up ahead?

It could be that the UHF noise hadn't been designed to kill ... only to annoy them and make them run faster, herding them like animals, straight into another trap.

Gotta watch it ... be ready.

He was still holding Ruth's hand, even though they had passed the danger.

As they ran along, he was surprised how good this felt.

Her hand in mine.

As they navigated the twists and turns of the cavern, he checked on Jordan and Annie, his backup.

Both appeared to have recovered, a little anyway, although Jordan's neck was streaked with blood.

Have to be ready for whatever's ahead.

Then ... he tensed when, up ahead, he saw that the cavern looked like it had come to an end.

A dead end ... or worse?

He slowed his pace, and Ruth, breathing heavily behind him, slowed down as well. Even when they stopped, Ivan noticed how neither of them let go of the other's hand.

The cavern narrowed down, and there was a wall of blackness ahead.

"Hold up!" he shouted, and now-finally-he reluctantly let go of Ruth's hand.

Sinjira and the rest of them came to a halt.

"What is it?" Annie asked.

"Dead end. Maybe," Ivan said.

Up ahead, he saw a dark entryway, blocked by three huge stones, stacked one on top of the other ... like stairs.

At the top, a platform.

Ivan approached the opening, staring into the darkness beyond. Jordan came up beside him and lit a flare.

"Looks like it drops off on the other side," Ivan said. "I wish we still had a flashlight that worked."

Ivan climbed the three large stone steps to the top of the platform. Once he was at the top, he looked down.

And saw nothing but darkness.

"Shit."

"What is it?" Jordan asked, striding up the stairs behind him. They both peered down into what might as well have been a bottomless pit.

"Too dark even for the goggles."

"Totally black."

"Got another flare?" Ivan asked.

Without a word, Jordan slung his backpack off and opened the top flap.

"Only a few left," the gunner said.

As Jordan took out a flare, Ivan asked, "How many?"

"Seven ... counting this one."

Ivan nodded, thinking.

Jordan took out three flares and handed them to Ivan.

"Share and share alike."

"Thanks," Ivan said as he slipped them into his backpack and zipped it shut.

He watched as Jordan struck the second flare and held it above his head. The sputtering red glow filled the cavern as sparks spilled to the floor and a thick billow of smoke rose to the dark reaches of the cave ceiling. How far up it went was anyone's guess.

The sudden brightness momentarily blinded Ivan, but when he looked down, he could see ...

"I'll be a son of a bitch," he said as he and Jordan stared down at the long flight of stone steps spiraling down into the depths below.

Ivan looked back at the others and called out. "There's a stairway. We have to go down."

Is that all this is? he wondered.

He took the first step down, placing his foot solidly on the wide stone.

And in an instant, it disappeared ... like a light winking off.

Thrown off balance, Ivan lurched forward and began to fall.

38.