Ambrose stared at the skull, a vague look in his eyes. "It would take a laboratory to determine if it was cut and polished by hand or with modern tools. The only fact we know for certain is that this room was not excavated and created by miners. There would have to be an account somewhere of such an extensive project. Marquez assures me that old Paradise Mine records and tunnel maps show nothing indicating a vertical shaft leading to an underground chamber in this particular location. So it must have been excavated prior to 1850."

"Or much later."

Ambrose shrugged his shoulders. "All mining operations were shut down in 1931. A major operation such as this could not have gone unnoticed since then. I'm reluctant to lay my reputation on the line, but I'll state without equivocation that I firmly believe this chamber and the skull are more than a thousand years old, probably much older."

"Perhaps early Indians were responsible," Pat persisted.

Ambrose shook his head. "Not possible. The early Americans built a number of complex stone structures, but an enterprise of this precise magnitude was beyond them. And then you have the inscriptions. Hardly the work of people without a written language."

"This does appear to have the hallmark of a high intelligence," she said softly, her fingertips lightly tracing the symbols in the granite.

With Ambrose at her side, Pat began copying the unusual symbols in a small notebook until she could account for a total of forty-two. Then she measured the depth of the engravings and the distance between the lines and the symbols. The more she examined the apparent wording, the more perplexed she became. There was a mysterious logic about the inscriptions that only a meticulous translation could solve. She was busily taking flash photos of the inscriptions and star symbols in the ceiling when Marquez climbed through the hole in the floor.

"Looks like we're going to be here for a while, folks," he announced. "An avalanche has covered the mine entrance."

"Oh, dear God," muttered Pat.

"Not to fret," Marquez said with a tight grin. "My wife has gone through this before. She'll be aware of our predicament and will have called for help. A rescue unit from town will soon be on its way with heavy equipment to dig us out."

"How long will we be trapped here?" asked Ambrose.

"Hard to say without knowing how much snow is blocking the shaft opening. Could be only a few hours. Might take as long as a day. But they'll work around the clock until they clear away the snow. You can bet on it."

A sense of relief settled over Pat. "Well, then, as long as your lights are still working, I suppose Dr. Ambrose and I can spend the time recording the inscriptions."

The words were barely out of her mouth when a tremendous rumble rose from somewhere deep beneath the chamber. Then the grinding sound of crashing timbers, followed by the deep growl of falling rock, reverberated from the tunnel. A violent rush of air roared through the cleft and into the chamber as they were all pitched headlong onto the rock floor.

Then the lights blinked out.

The rumble deep within the mountain echoed ominously from the hidden reaches of the tunnel and slowly faded away into a smothering silence, while unseen in the pitch blackness, dust disturbed by the concussion rolled through the tunnel, into the cleft, and up through the opening of the chamber like an invisible hand. Then came the sounds of coughing as the dust clogged noses and mouths, the grit quickly clinging to their teeth and tongues.

Ambrose was the first to gasp out coherent words. "What in God's name happened?"

"A cave-in," rasped Marquez. "The roof of the tunnel must have collapsed."

"Pat!" Ambrose shouted, feeling around in the darkness. "Are you hurt?"

"No," she managed between fits of coughing. "The breath was knocked out of me, but I'm all right."

He found her hand and helped her to her feet. "Here, take my handkerchief and hold it to your face."

Pat stood quite still as she fought to get a clean breath. "It felt as if the earth exploded beneath my feet."

"Why did the rock suddenly give way?" Ambrose asked Marquez, unable to see him.

"I don't know, but it sounded like a dynamite blast to me."

"Couldn't the aftershock of the avalanche have caused the tunnel to collapse?" asked Ambrose.

"I swear to God, it was dynamite," said Marquez. "I ought to know. I've used enough of it over the years to recognize the sound. I always use low particle-velocity dynamite to minimize ground shock. Someone set off a charge with concentrated powder in one of the tunnels beneath this one. A big one, judging from the shock."

"I thought the mine was abandoned."

"It was. Except for my wife and myself, no one has set foot in here for years."

"But how-"

"Not how, but why?" Marquez brushed by the anthropologist's legs as he crawled on all fours searching for his hard hat.

"Are you saying that someone purposely set off explosives to seal the mine?" Pat asked, bewildered.

"I'll damn well find out if we get out of here." Marquez found his hat, set it over his dust-coated hair, and switched on the little light. "There, that's better."

The little light gave but token illumination inside the chamber. The settling dust had the eerie and forbidding look of a waterfront fog. They all looked like statues under the dust, their faces and clothing the color of the surrounding gray granite.

"I don't care for the way you said `if.' "

"Depends on which side of the cleft the tunnel collapsed. Farther into the mine, we'll be clear. But if the roof fell somewhere between here and the exit shaft, we have a problem. I'll go and take a look."

Before Pat could say another word, the miner had slipped through the hole and the chamber was thrown back into absolute darkness. Ambrose and Pat stood silent in a sea of suffocating blackness, the initial traces of terror and panic seeping into their minds. Less than five minutes had passed before Marquez returned. They could not see his face because of the beam from his hard hat light in their eyes, but they sensed that he was a man who had seen and touched doom.

"I'm afraid the news is all bad," he said slowly. "The cave-in is only a short distance down the tunnel toward the shaft. I estimate that the fall extends a good thirty yards or more. It'll take days, maybe weeks for rescuers to clear the rubble, timbering as they go."

Ambrose stared closely at the miner, searching for any expression of hope. Seeing none, he said, "But they will get us out before we starve?"

"Starving isn't our problem," Marquez said, unable to hide the tone of despair that had crept into his voice. "Water is rising in the tunnel. It's already flooded up to three feet."

It was then Pat saw that Marquezs pants up to his knees were soaking wet. "Then we're trapped in this hellhole with no way out?"

"I didn't say that!" the miner snapped back. "There's a good chance the water will run off into a crosscut tunnel before reaching the chamber."

"But you can't be sure," said Ambrose.

"We'll know in the next few hours," Marquez hedged.

Pat's face was pale and her breath was coming slowly through lips tainted with the dust. She became gripped with cold fear as she heard the first sounds of the water swirling outside the chamber. At first the volume had not been great, but it was increasing rapidly. Her eyes met Ambrose's gaze. He could not hide the dread that was written in his face.