The Empty Chair

However, the problem with dirt as evidence is that it's too prevalent. In order for it to have any meaning forensically a bit of dirt whose source might be the criminal must be different from the dirt found naturally at the crime scene.

The first step in dirt analysis is to check known soil from the scene – an exemplar – against the sample the criminalist believes came from the perp.

Rhyme explained this to Ben and the big man picked up one bag of dirt, which Sachs had marked Exemplar soil – Blackwater Landing, along with the date and time of collection. There was also a notation in a hand that was not Sachs'. Collected by Deputy J. Corn. Rhyme pictured the young deputy eagerly scurrying off to do her bidding. Ben poured some of this dirt onto a third subscription card. He set it beside the dirt he'd dug out of Garrett's treads. "How do we compare them?" the young man asked, looking over the instruments.

"Your eyes."

"But – "

"Just look at them. See if the color of the unknown sample is different from the color of the known."

"How do I do that?"

Rhyme forced himself to answer calmly. "You just look at them."

Ben stared at one pile, then the other.

Back again. Once more.

And then once again.

Come on, come on… it isn't that tricky. Rhyme struggled to be patient. One of the hardest things in the world for him.

"What do you see?" Rhyme asked. "Is the dirt from the two scenes different?"

"Well, I can't exactly tell, sir. I think one's lighter."

"'Scope them in the comparison."

Ben mounted the samples in a comparison microscope and looked through the eyepieces. "I'm not sure. Hard to say. I guess… maybe there is some difference."

"Let me see."

Once again the massive muscles held the large microscope steady and Rhyme peered into the eyepieces. "Definitely different from the known," Rhyme said. "Lighter-colored. And it has more crystal in it. More granite and clay and different types of vegetation. So it's not from Blackwater Landing… If we're lucky it came from his hidey-hole."

A faint smile crossed Ben's lips, the first Rhyme had seen.

"What?"

"Oh, well, that's what we call the cave a moray eel takes for his home…" The young man's smile vanished as Rhyme's stare told him that this was not the time or place for anecdotes.

The criminalist said, "When you get the results of the limestone on the chromatograph run the dirt from the treads."

"Yessir."

A moment later the screen of the computer attached to the chromatograph/spectrometer flickered and lines shaped like mountains and valleys appeared. Then a window popped up and the criminalist maneuvered closer in his wheelchair. He bumped a table and the Storm Arrow jerked to the left, jostling Rhyme. "Shit."

Ben's eyes went wide with alarm. "Are you all right, sir?"

"Yes, yes, yes," Rhyme muttered. "What's that fucking table doing there? We don't need it."

"I'll get it out of the way," Ben blurted, grabbing the heavy table with one hand as if it were made of balsa wood and stashing it in the corner. "Sorry, I should've thought of that."

Rhyme ignored the zoologist's uncomfortable contrition and sca

This was very troubling but Rhyme said nothing just yet; he wanted to see what substances were in the dirt that Ben had dug out of the treads. And shortly these results too were on the screen.

Rhyme sighed. "More nitrates, more ammonia – a lot of it. High concentrations again. Also, more phosphates. Detergent too. And something else… What the hell is that?"

"Where?" Ben asked, leaning toward the screen.

"At the bottom. The database's identified it as camphene. You ever hear of that?"

"No, sir."

"Well, Garrett walked through some of it, whatever it is." He looked at the evidence bag. "Now, what else do we have? That white tissue Sachs found…"

Ben picked up the bag, held it close to Rhyme. There was a lot of blood on the tissue. He glanced at the other tissue sample – the Kleenex that Sachs had found in Garrett's room. "They the same?"

"Look the same," Ben said. "Both white, both the same size."

Rhyme said, "Give them to Jim Bell. Tell him I want a DNA analysis. The drive-through variety."

"The, uhm… what's that, sir?"

"The down-and-dirty DNA, the polymerase chain reaction. We don't have time for the RFLP – that's the one-in-six-billion version. I just want to know if it's Billy Stail's blood or somebody else's. Have somebody scrounge up samples from Billy Stail's body and from Mary Beth and Lydia."

"Samples? Of what?"

Rhyme forced himself once more to remain patient. "Of genetic material. Any tissue from Billy's body. For the women, getting some hair would be the easiest – as long as the bulb's attached. Have a deputy pick up a brush or comb from Mary Beth's and Lydia 's bathrooms and get it over to the same lab that's ru

The man took the bag and left the room. He returned a moment later. "They'll have it in an hour or two, sir. They're going to send it to the med center in Avery, not to the state police. Deputy Bell, I mean, Sheriff Bell, thought that would be easier."

"An hour?" Rhyme muttered, grimacing. "Way too long."

He couldn't help wondering if this delay might be just long enough to keep them from finding the Insect Boy before he killed Lydia or Mary Beth.

Ben stood with his bulky arms at his sides. "Uhm, I could call them back. I told 'em how important it was but… Do you want me to?"

"That's okay, Ben. We'll keep going here. Thom, time for our charts."

The aide wrote on the blackboard as Rhyme dictated to him.

FOUND AT PRIMARY CRIME SCENE -

BLACKWATER LANDING

Kleenex with Blood

Limestone Dust

Nitrates

Phosphate

Ammonia

Detergent

Camphene

Rhyme gazed at it. More questions than answers…

Fish out of water…

His eye fell on the pile of dirt that Ben had dug out of the boy's shoe. Then something occurred to him. "Jim!" he shouted, his voice booming and startling both Thom and Ben. "Jim! Where the hell is he? Jim!!"

"What?" The sheriff came ru

"How many people work in the building here?"

"I don't know. 'Bout twenty."

"And they live all over the county?"

"More'n that. Some travel from Pasquotank, Albemarle and Chowan."

"I want 'em all down here now."

"What?"

"Everybody in the building. I want soil samples from their shoes… Wait: And the floor mats in their cars."

"Soil…"

"Soil! Dirt! Mud! You know. I want it now!"

Bell retreated. Rhyme said to Ben, "That rack? Over there?"

The zoologist lumbered toward the table on which was a long rack holding a number of test tubes.

"It's a density-gradient tester. It profiles the specific gravity of materials like dirt."

He nodded. "I've heard of it. Never used one."

"It's easy. Those bottles there -" Rhyme was looking toward two dark glass bottles. One labeled tetra, the other ethanol. "You're going to mix those the way I tell you and fill up the tubes close to the top."

"Okay. What's that going to do?"

"Start mixing. I'll tell you when we're through."

Ben mixed the chemicals according to Rhyme's instructions and then filled twenty of the tubes with alternating bands of different-colored liquids – the ethanol and the tetrabromoethane.

"Pour a little of the soil sample from Garrett's shoe into the tube on the left. The soil'll separate and that'll give us a profile. We'll get samples from employees here who live in different areas of the county. If any of them match Garrett's that means the dirt he picked up could be from nearby."