“Dr. Paden, I was told you were one of the world’s foremost experts on turquoise. I can see already that I was not deceived.”

Paden inclined his head. He was surprised to meet someone from law enforcement as insightful, and as gentlemanly, as this fellow.

“But you see, Dr. Paden, I need to know the exact mine it came from.”

As he spoke, the pale FBI agent looked at him most intensely. Paden smoothed his hand over his bald pate. “Well, Mr., ah, Pendergast, that’s a horse of a different color.”

“How so?”

“If I can’t recognize the source mine from an initial visual examination — and in this case I can’t — then testing of the specimen would be required. You see—” and here Paden drew himself up as he launched into his favorite subject—“turquoise is a hydrous phosphate of copper and aluminum, which forms by the percolation of water through a rock with many cavities and empty spaces, usually volcanic. The water carries dissolved copper sulfides and phosphorous, among other things, which precipitate in the interstices as turquoise. Southwestern turquoise almost invariably occurs where copper sulfide deposits are found among potassium feldspar bearing porphyritic intrusives. It can also contain limonite, pyrites, and other iron oxides.” He rose and, moving fast on stubby legs, walked to a massive cabinet, bent over, and pulled open a drawer. “Here you see a small but exquisite collection of turquoise, all from prehistoric mines. We use it to help archaeologists identify the source of prehistoric turquoise artifacts. Come, take a look.”

Paden waved the agent over, then took the turquoise sample from him and rapidly compared it with others in the drawer. “I don’t see anything close to a match here, but turquoise can vary in appearance even from one part of a mine to another. And this is only a small sampling. Take this piece of Cerrillos turquoise, for example, from the Cerrillos mines south of Santa Fe. This rare piece comes from the famed prehistoric site known as Mount Chalchihuitl. It’s ivory with a pale-lime matrix, of great historical value, even if it isn’t the finest quality. And here we have examples of prehistoric turquoise from Nevada—”

“How terribly interesting,” Pendergast said smoothly, stemming the flow of words. “You mentioned testing. What sort of testing would be necessary?”

Paden cleared his throat. It had been mentioned to him more than once that he had a tendency to run on. “What I’ll have to do is analyze your stone — turquoise and matrix — using various means. I’ll start with proton-induced X-ray emission analysis, in which the stone is bombarded with high-speed protons in a vacuum, and the resulting X-ray emission analyzed. Fortunately, here at the Museum we have an excellent mineralogy lab. Would you care to see it?” He beamed at Pendergast.

“No, thank you,” said Pendergast. “But I’m delighted you’re willing to do the work.”

“But of course! This is what I do. Mostly for archaeologists, of course, but for the FBI–I am at your service, Mr. Pendergast.”

“I almost forgot to mention to you my little problem.”

“Which is?”

“I need the work done by noon tomorrow.”

“What? Impossible! It will take weeks. A month, at least!”

A long pause. “But would it be physically possible for you to complete the analysis by tomorrow?”

Paden felt his scalp prickle. He wasn’t sure that this man was quite as pleasant and easygoing as he seemed at first. “Well.” He cleared his throat. “It’s physically possible, I suppose, to get some preliminary results by then, but it would mean working nonstop for the next twenty hours. And even then I might not succeed.”

“Why not?”

“It would all depend on whether this particular type of turquoise has been analyzed before, with its chemical signature recorded in the database. I’ve done quite a lot of turquoise analyses for archaeologists, you see. It helps them figure out trade routes and so forth. But if this piece comes from a newer mine, we might never have analyzed it. The older the mine, the better the chance.”

A silence. “May I ask you, Dr. Paden, to kindly undertake this task?”

Paden smoothed his pate again. “You’re asking me to stay up for the next twenty hours, working on your problem?”

“Yes.”

“I have a wife and children, Mr. Pendergast! Today’s a Sunday — normally I wouldn’t even be here. And I am not a young man.”

The agent seemed to take this in. Then, with a languid motion, he reached into his pocket and removed something, again holding it in his closed hand. He reached out and opened the hand. Inside was nestled a small, glittering reddish-brown cut stone of about a carat. Instinctively, Paden reached out to take it, screwed the loupe into his eye, and examined it, turning it this way and that. “Oh my. Oh my, my. Strongly pleochroic…” He grabbed a small, handheld UV light from the table and switched it on. The stone instantly changed color, becoming a brilliant neon green.

He looked up, his eyes wide. “Painite.”

The FBI agent bowed his head. “I was not deceived in thinking you were a most excellent mineralogist.”

“Where in heaven’s name did you get this?”

“My great-grand-uncle was a collector of oddities, which I inherited along with his house. I plucked this from his collection, as an inducement. It’s yours — provided you accomplish the task at hand.”

“But this stone must be worth… good heavens, I hesitate to even put a price on it. Painite is one of the rarest gemstones on earth!”

“My dear Dr. Paden, the information on what mine that turquoise came from is far more precious to me than that stone. Now: can you do it? And,” he added dryly, “are you sure your wife and children won’t object?”

But Paden was already on his feet, placing the turquoise in a ziplock bag and thinking ahead to the many chemical and mineralogical tests he would need to perform. “Object?” he said over his shoulder as he departed into the inner sanctum of his laboratory. “Who the hell cares?”

After three wrong turns and two stops to ask directions, Lieutenant D’Agosta finally managed to find his way out of the maze of the Osteology Department and down to the ground floor. He crossed the Great Rotunda toward the entrance, walking slowly, deep in thought. His meeting with the chief curator, Morris Frisby, had been a waste of time. None of the other interviews had shed much light on the murder. And he had no idea how the perp effected egress from the Museum.

He’d been wandering the Museum since early that morning, and now both his feet and the small of his back ached. This was looking more and more like a typical piece-of-shit New York City murder case, random and brainless — and as such, a pain in the ass to clear. None of the day’s leads had panned out. The consensus was that Victor Marsala had been an unpleasant person but a good worker. Nobody at the Museum had reason to kill him. The only possible suspect — Brixton, the bat scientist, who’d had a row with Marsala two months before — had been out of the country at the time of the murder. And besides, a weenie like that just wasn’t the type. Members of D’Agosta’s team had already interviewed Marsala’s neighbors in Sunnyside, Queens. They all labeled him as quiet, a loner who kept to himself. No girlfriend. No parties. No drugs. And quite possibly no friends, except perhaps the Osteology technician, Sandoval. Parents lived in Missouri, hadn’t seen their son in years. The body had been found in an obscure, rarely visited section of the Museum, missing wallet, watch, and pocket change. There was little doubt in D’Agosta’s mind: this was just another robbery gone bad. Marsala resisted and the dumb-ass perp panicked, killed him, and dragged him into the alcove.

To make matters worse, there was no lack of evidence — if anything, D’Agosta and his team were already drowning in it. The crime scene was awash in hair, fiber, and prints. Thousands of people had tramped through the hall since it was last mopped and the cases wiped down, leaving their greasy traces everywhere. He had a brace of detectives reviewing the Museum’s security videos, but so far they’d found nothing suspicious. Two hundred employees had worked late last night — so much for taking weekends off. D’Agosta could see it now, all too plainly: he’d beat his head against the case for another week or two, wasting his time in vain dead-end investigations. Then the case would be filed and slowly grow cold, another squalid unsolved homicide, with its megabytes of interview transcripts, digitized photos, and SOC analyses washing around the NYPD’s database like dirty water at the base of a pier, serving no purpose other than dragging down his clearance rate.