Fifteen minutes later, they were sitting in the ore cart, making the descent from the portal into the old Paradise Mine. It was a new experience for Pat. She had never entered a mine shaft.

"It feels warmer," she observed, "the deeper we go."

"As a rule of thumb," explained Marquez, "the temperature increases by five degrees every hundred feet you descend into the earth. In the lower levels of the mine that are now flooded, the heat used to be over a hundred degrees."

The ore cart came to a stop. Marquez climbed out and dug into a large wooden toolbox. He handed Pat and Ambrose each a hard hat.

"For falling rock?" asked Pat.

Marquez laughed. "Mostly to keep your scalp from knocking against low timbers."

The dim yellow lights attached to the overhead timbers flickered overhead as they made their way through the damp tunnel with Marquez in the lead. When one of them spoke, the voice sounded hollow against the surrounding rock walls of the tunnel. Pat stumbled more than once on the ties holding the old rusting ore cart rails, but caught herself before falling. She hadn't realized when she'd dressed earlier in the morning, before flying to Telluride, what a wise decision it was to wear a pair of comfortable hiking shoes. After what seemed an hour but was actually only ten minutes, they reached the cleft leading to the chamber and followed Marquez through the narrow passage.

He stopped at the ladder and motioned upward to where a bright light spilled through the opening in the rock ceiling. "I strung lights inside since you visited yesterday, Dr. Ambrose. The sheer walls act as reflectors, so you shouldn't have a problem studying the writing." Then he stood aside and helped Pat up the ladder.

Not having been told what to expect, she was stunned. She felt like Howard Carter when he first viewed King Tuts tomb. Her eyes immediately locked on the black skull, and she reverently approached its pedestal and stared at the smooth surface gleaming under the lights.

"It's exquisite," she murmured admiringly, as Ambrose squeezed through the opening and stood beside her.

"A masterwork," he agreed. "Carved out of obsidian."

"I've seen the Mayan crystal skull that was found in Belize. This one is far more inspiring. The other is crude in comparison."

"They say the crystal skull emits an aura of light, and strange sounds are heard to come from it."

"It must have been lethargic the time I studied it," said Pat, smiling. "It only sat there and stared."

"I can't imagine how many years- generations most likely, without modern tools- it took to polish such an object of beauty from a mineral so brittle. One tap of a hammer and it would shatter into a thousand pieces."

"The surface is so smooth, it's flawless," Pat said softly.

Ambrose swept one hand around the chamber. "This entire chamber is a wonder. The inscriptions on the walls and ceiling must easily have taken five men a lifetime to engrave in the rock, but not before an immense effort was spent polishing the interior surfaces. This chamber alone had to have taken years to carve out of solid granite at this depth. I've measured the dimensions. The four walls, floor, and ceiling enclose a perfect cube. If the interior surfaces are out of alignment or plumb, it's less than one millimeter. Like the classic old mystery novel, we have a drama that took place in a room with no windows or doors."

"The opening in the floor?" Pat asked.

"Blasted by Luis Marquez while excavating for gemstones," replied Ambrose.

"Then how was this chamber created without an entrance and exit?"

Ambrose pointed to the ceiling. "The only hint I could find of an infinitesimal crack around the borders was in the ceiling. I can only assume that whoever constructed this cubicle burrowed down from above and placed a precisely carved slab atop the cubicle."

"For what purpose?"

Ambrose grinned. "The reason why you're here, to find answers."

Pat removed a notepad, a small paintbrush and a magnifying glass from a pack she carried on her belt. She moved close to one wall, gently swept away the dust of centuries from the rock, and peered at the script through the glass. She intently studied the markings for several moments before looking up and staring at the ceiling. Then she looked at Ambrose with a blank expression in her face. "The ceiling appears to be a celestial map of the stars. The symbols are…" She hesitated and stared at Ambrose with a blank expression. "This must be some sort of hoax perpetrated by the miners who dug the tunnel."

"What brought you to that conclusion?" inquired Ambrose.

"The symbols don't bear the slightest resemblance to any ancient writings I've ever studied."

"Can you decipher any of them?"

"All I can tell you is that they are not pictographic like hieroglyphics, or logographic signs that express individual words. Nor do the symbols suggest words or oral syllables. It appears to be alphabetic."

"Then they're a combination of single sounds," offered Ambrose.

Pat nodded in agreement. "This is either some sort of written code or an ingenious system of writing."

Ambrose looked at her intently. "Why do you think this is all a hoax?"

"The inscriptions do not fit any known pattern set down by man throughout recorded history," Pat said in a quiet, authoritative voice.

"You did say ingenious."

Pat handed Ambrose her magnifying glass. "See for yourself. The symbols have a remarkable simplicity. The use of geometric images in combination with single lines is a very efficient system of written communication. That's why I can't believe any of this comes from an ancient culture."

"Can the symbols be deciphered?"

"I'll know after I make tracings and run them through the computer lab at the university. Most ancient inscriptions are not nearly as definite and distinct as these. The symbols appear to have a well-defined structure. The main problem is that we have no other matching epigraphs anywhere else in the world to act as a guide. I'm treading in unknown waters until the computer can make a breakthrough."

"How you doin' up there?" Marquez shouted from the cleft below.

"All done for now," Pat answered. "Do you have a stationer's store in town?"

"Two of them."

"Good. I'll need to buy a ream of tracing paper and some transparent tape to make long sheets I can roll-" She fell silent as a faint rumble issued from the tunnel and the floor of the cubicle trembled beneath their feet.

"An earthquake?" Pat called down to Marquez.

"No," he replied through the hole. "My guess is an avalanche somewhere on the mountain. You and Dr. Ambrose go on about your business. I'll run topside and check it out."

Another tremor shook the chamber with a stronger intensity than the last one.

"Maybe we should go with you," Pat said apprehensively.

"The tunnel support timbers are old, and many are rotten," warned Marquez. "Excessive movement of the rock could cause them to collapse, produce a cave-in. It's safer if you two wait here."

"Don't be long," said Pat. "I feel a touch of claustrophobia coming on."

"Back in ten minutes," Marquez assured her.

As soon as Marquezs footsteps faded from the cleft below, Pat turned to Ambrose. "You didn't tell me your appraisal of the skull. Do you think it ancient or modern?"