Rainwater looked like the old professor from a Disney movie. Baggy sweater, bad haircut, wire-rimmed specs. The only thing that didn’t fit was the snazzy new Mac where he was working.

The office was a claustrophobic’s worst nightmare. An enormous desk and bulky file cabinets left only narrow passages for navigation about the small space. Every shelf and horizontal surface was covered with stacked papers and magazines, rolled maps, hunks of rock and petrified wood, and glass containers holding gravel and sand. If anything hung on a wall, it was hidden from view.

I cleared my throat.

Rainwater looked up. “Yes?”

“My name is Temperance Brennan. I have a few questions and was told you were very knowledgeable.”

“What kind of questions?”

“About prospecting.” Cautious.

“A prospector’s license is two dollars for an individual, fifty for a company. The girl out front can help you with that on Monday.”

Rainwater’s eyes returned to the screen. His fingers resumed their hunt-and-peck ballet.

“If you need a prospecting permit, you’re out of luck. Applications are accepted in December. Approved permits are issued effective February first of the following year. Permits are good for three years below the Sixty-eighth parallel, five years above. The cost is twenty-five dollars plus ten cents an acre.” Rainwater’s tone was robotic, suggesting he’d repeated the information thousands of times. “A prospecting permit gives you temporary but exclusive exploration and staking rights but not mineral rights.”

“Sir, I—”

“You need a valid prospector’s license to stake a claim but don’t need a prospecting permit. A claim requires four tagged posts. Tags cost two dollars a set. The girl out front can sell you those on Monday.”

“Mr. Rainwater—”

“It’s mandatory to check with this office before staking a claim to make sure the area is available and not already staked, claimed, or leased by someone else. The girl out front can—”

“I also want to learn about diamond indicator minerals.”

Rainwater’s eyes rolled up. He studied me through the upper portion of old-fashioned bifocal lenses. “What about them?”

I pulled the ketchup container from my purse. “I have a sample.” Lay it on. “I know this is irregular, and I know I’m being presumptuous, but your nephew says you’re a genius with these things.”

“You a friend of Joseph’s?”

“Mm.”

Rainwater hesitated, then waggled me in with upturned fingers.

As I wormed my way forward, he cleared space on his blotter, unfolded a white cloth, and spread it flat with his palms. Then he exchanged the bifocals for glasses with a little microscope stuck to each lens.

I gave him the purloined sample. He poured the gravel onto the cloth, turned on and adjusted a lamp clamped to one side of his desk, and leaned in.

I waited.

Every now and then Rainwater poked at the sample, rearranging the mix with one gnarled finger.

Long minutes passed. The entire floor was absolutely still.