"No, I'm serious," Pat said firmly. "I swear it sounds like a motorcycle."

Then Pitt heard something, too. He turned and faced the tunnel from the direction they had come and cupped his hands to his ears. He made out the undeniable sound of exhaust from a high-performance off-road motorcycle. He stared soberly at Marquez. "Do the locals ride around old mine tunnels on motocross dirt bikes for a thrill?"

Marquez shook his head. "Never. They'd become lost in a maze of tunnels, if they didn't plunge down a thousand-foot shaft first. Then there's the danger of their exhaust noise causing rotted beams to collapse and a cave-in to crush them. No, sir, nobody I know is fool enough to joyride underground."

"Where did they come from?" Pat asked no one in particular.

"From another mine that's still accessible. Lord only knows how they happened to be in the same tunnel as we are."

"A peculiar coincidence," Pitt said, staring up the tunnel. He felt a sense of uneasiness. Why? He couldn't be sure. He stood without moving a muscle, listening to the rattling sound of the exhaust as it grew louder. It was a foreign sound in the old mine labyrinth. It did not belong. He stood still as the first flash of light showed far down the tunnel.

Pitt couldn't tell yet if it was one or more motorcycles coming through the tunnel. It seemed a reasonable assumption that he should treat the biker or bikers as a threat. Better safe than sorry. As ancient and hackneyed as the words sounded, they still had meaning, and his cautious nature had saved him on more than one occasion.

He turned and slowly walked past Ambrose and Marquez. Absorbed in the approach of the sound and lights, they took no notice as he slipped along one wall of the tunnel in the direction of the approaching bikers. Only Pat focused on Pitt as he unobtrusively stole into the darkness of a portal leading into a narrow bore between the timbers. One moment he was there, the next he had vanished like a wraith.

There were three bikers. The front of their machines were packed with an array of halogen lights that blinded the exhausted survivors, who shielded their eyes with their hands and turned away as the engines slowed and idled in neutral. Two of the intruders dismounted their bikes and walked closer, their bodies silhouetted by the bright lights behind them. They looked like space aliens in their black, sleek helmets and two-piece jerseys worn under chest protectors. Their boots came halfway to their knees and their hands were encased in black, ribbed gloves. The third biker remained on his machine as the other two approached and raised the shields on their helmets.

"You don't know how happy we are to see you," said Pat excitedly.

"We sure could have used your help earlier," said Ambrose wearily.

"My compliments on making it this far," said the figure on the right, in a voice deep and sinister. "We thought sure you'd drowned in the Amenes chamber."

"Amenes?" Pat repeated, puzzled.

"Where did you guys come from?" demanded Marquez.

"It doesn't matter," said the biker, as if he were brushing off a classroom student's irrational question.

"You knew we were trapped in the chamber by a rockfall and rising water?"

"Yes," the biker said coldly.

"And you did nothing?" Marquez said incredulously. "You didn't try to rescue us or go for help?"

"No."

A stimulating conversationalist, this guy, thought Pitt. If he'd been a tiny bit suspicious earlier, he was downright convinced now that these men were not local daredevils on a weekend adventure. These men were killers, and heavily armed. He didn't know why, but he knew they were not going to allow them to escape the mines alive. It was time to act, and surprise was his only advantage. He slipped his dive knife from its sheath and gripped the hilt. It was the only weapon he had, and it would have to do. He took several slow deep breaths and gave a final flex to his fingers. It was now or never.

"We came within minutes of drowning in the chamber," said Pat, wondering what Pitt was planning, if anything. She began to wonder if he was a coward and simply hiding from danger.

"We know. That was the plan."

"Plan? What plan?"

"You all were supposed to die," the biker said conversationally.

The words were greeted with a stunned, uncomprehending silence. "Unfortunately, your will to survive overcame the cave-in and the flooding," the biker continued. "We did not foresee your perseverance. But it is of no matter. You merely prolonged the inevitable."

"The dynamite blast," muttered Marquez in shock. "That was you?"

The answer was candid. "Yes, we set the charge."

Pat began to look like a deer staring into the headlights of an approaching truck. She knew that the bikers were not aware of Pitt's presence, so she acted as if he didn't exist. Marquez and Ambrose assumed he was simply standing behind them quietly, as stunned with shock as they were.

"Why would you want to kill us?" she asked, her voice shaking. "Why would total strangers want to murder us?"

"You saw the skull and you saw the inscriptions."

Marquez looked like a man torn between fear and anger. "So what?" he growled.

"Your discovery cannot be allowed to become known outside these mines."

"We've done nothing wrong," Ambrose said, strangely calm. "We're scientists studying historic phenomena. We're not talking treasure but ancient artifacts. It's insane to be killed because of it."

The biker shrugged. "It's unfortunate, but you became involved with matters far beyond your comprehension."

"How could you possibly know about our entry into the chamber?" asked Marquez.

"We were informed. That's all you need to know."

"By who? Not more than five people knew we were there."

"We're wasting time," grunted the second biker. "Let's finish our business and throw them down the nearest shaft."

"This is madness," muttered Ambrose, with little or no feeling in his voice.

Pitt silently moved from the bore, any sounds of his footsteps covered by the soft popping from the exhaust, and crept up behind the rider still sitting on his bike, who was distracted by the conversation. Pitt was no stranger to killing, but it wasn't in him to knife another man in the back, no matter how rotten the victim might be. In the same motion, he reversed the grip on the knife and plunged the blunt hilt with all his strength against the base of the biker's neck below the helmet. It bordered on a killing blow, but it was a pound short of fatal. The biker sagged in his seat and fell back against Pitt without making so much as a soft moan. Pitt crouched low and quickly threw his arms around the body, held it for a moment, then lowered it, together with the bike, quietly onto the ore cart track with the engine still idling in neutral.

Working swiftly, he pushed aside the biker's chest protector and uncased a Para-Ordnance 10+1 round,45-caliber automatic from a shoulder holster strapped under an armpit. He trained the sights on the back of the biker standing on his right and pulled back the hammer. He had never fired a P-10 before, but from the feel, he knew the magazine was full and that the gun possessed most of the same features as his trusty old Colt .45, which was locked inside the NUMA vehicle he'd driven to Colorado from Washington.

The headlights on the motorcycles brightly illuminated the two killers, who failed to detect the figure stealing up behind them, but as Pitt crept closer, he passed in front of the light from the third bike, which was lying on the track, and he became identifiable to Ambrose.