Lucy walked up to his door. "Hey Pete," she said, "you need to wash your ride."

"No, I don't," he grumbled as he immediately tossed the cigarette and got out.

He looked around, and the sight of him hitching up his pants and inspecting his car because he could not help himself was too much. Lucy and I both laughed, and then he tried not to smile. In truth, he secretly enjoyed it when we teased. We bantered a little bit more, and then Lucy left as a late-model gold Lexus with tinted glass drove past. It was the same one we had seen earlier on the road, the driver obliterated by glare.

"This is beginning to get on my nerves." Marino's eyes followed the car.

"Maybe you should run the plate number," I stated the obvious.

"Oh, I already done that." He started the car and began backing out. -DMV's down."

DMV was the Department of Motor Vehicles computer, and it was down a lot, it seemed. We headed back up to the reactor facility, and when we got there, Marino again refused to go inside. So I left him in the parking lot, and this time the young man in the control room behind glass told me I could enter unescorted.

"He's down in the basement," he said with eyes on his computer screen.

I found Matthews in the low background counting room again, sitting before a computer screen displaying a spectrum in black and white.

"Oh, hello," he said, when he realized I was beside him.

"Looks like you've had some luck," I said. "Although I'm not sure what I'm seeing. And I might be too early."

"No, no, you're not too early. These vertical lines here indicate the energies of the significant gamma rays detected. One line equals one energy. But most of the lines we're seeing here are for background radiation." He showed me on the screen. "You know, even the lead bricks don't get rid of all of that."

I sat next to him.

"I guess what I'm trying to show you, Dr. Scarpetta, is that the sample you brought in isn't giving off high-energy gamma rays when it decays. If you look here on this energy spectrum-he was staring at the screen-it looks like this characteristic gamma ray on the spectrum is for uranium two-thirty-five." He tapped a spike on the glass.

"Okay," I said. "And what does that mean?"

"That's the good stuff." He looked over at me.

"Such as is used in nuclear reactors," I said.

"Exactly. That's what we use to make fuel pellets or rods. But as you probably know, only point three percent of uranium is two-thirty-five. The rest is depleted."

"Right. The rest is uranium two-thirty-eight," I said.

"And that's what we've got here."

"If it isn't giving off high-energy gamma rays," I said.

How can you tell that from this energy spectrum?"

"Because what the germanium crystal is detecting is uranium two-thirty-five. And since the percentage of it is so low, this indicates that the sample we're dealing with must be depleted uranium."

"It couldn't be spent fuel from a reactor," I thought out loud.

"No, it couldn't," he said. "There's no fission material mixed in with your sample. No strontium, cesium, iodine, barium. You would have already seen those with SEM."

"No isotopes like that came up," I agreed. "Only uranium and other nonessential elements that you might expect with soil tracked in on the bottom of someone's shoes."

I looked at peaks and valleys of what could have been a scary cardiogram while Matthews made notes.

"Would you like printouts of all of this?" he asked.

"Please. What is depleted uranium used for?"

"Generally, it's worthless." He hit several keys.

"if it didn't come from a nuclear power plant, then from where?"

"Most likely a facility that does isotopic separation."

"Such as Oak Ridge, Tennessee," I suggested.

"Well, they don't do that anymore. But they certainly did for decades, and they must have warehouses of uranium metal. Now there also are plants in Portsmouth, Ohio, and Paducah, Kentucky."

"Dr. Matthews," I said. "It appears someone had depleted uranium metal on the bottom of his shoes and tracked it into a car. Can you give me any logical explanation as to how or why?"

"No." His expression was blank. "I don't think I can."

I thought of the jagged and spherical shapes the scanning electron microscope had revealed to me, and tried again.

"Why would someone melt uranium two-thirty-eight? Why would they shape it with a machine?"

Still, he did not seem to have a clue.

"is depleted uranium used for anything at all?" I then asked.

"In general, big industry doesn't use uranium metal," he answered. "Not even in nuclear power plants, because in those the fuel rods or pellets are uranium oxide, a ceramic."

"Then maybe I should ask what depleted uranium metal could, in theory, be used for," I restated.

"At one time there was some talk by the Defense Department about using it for armor plating on tanks. And it's been suggested that it could be used to make bullets or other types of projectiles. Let's see. I guess the only other thing we know that it's good for is shielding radioactive material."

"What sort of radioactive material?" I said as my adrenal glands woke up. "Spent fuel assemblies, for example?"

"That would be the idea if we knew how to get rid of nuclear waste in this country," he wryly said. "You see, if we could remove it to be buried a thousand feet beneath Yucca Mountain, Nevada, for example, then U-238 could be used to line the casks needed for transport."

"In other words," I said, "if the spent assemblies are to be removed from a nuclear power plant, they will have to be put in something, and depleted uranium is a better shield than lead."

He said this was precisely what he meant, and receipted my sample back to me, because it was evidence and one day could end up in court. So I could not leave it here, even though I knew how Marino would feel when I returned it to his trunk. I found him walking around, his sunglasses on.

"What now?" he said.

"Please pop the trunk."

He reached inside the car and pulled a release as he said. "I'm telling you right now, that it ain't going in no evidence locker in my precinct or at HQ. No one's going to cooperate, even if I wanted them to."

"it has to be stored," I simply said. "There's a twelvepack of beer in here."

"So I didn't want to have to bother stopping for it later."

"One of these days, you're going to get in trouble." I shut the trunk of his city-owned police car.

"Well, how about you store the uranium at your office," he said.

"Fine." I got in. "I can do that."

"So, how was it?" he asked, starting the engine.

I gave him a summary, leaving out as much scientific detail as I could.

"You're telling me that someone tracked nuclear waste into your Benz?" he asked, baffled.

"That's the way it appears. I need to stop by and talk to Lucy again."

"Why? What's she got to do with it?"

"I don't know that she does," I said as he drove down he mountain. "I have a rather wild idea."

I hate it when you get those."

Janet looked worried when I was back at their door, this time with Marino.

"Is everything all right?" she asked, letting us in.

"I think I need your help," I said. "Strike that. What I mean is that both of us do."

Lucy was sitting on the bed, a notebook open in her lap.

She looked at Marino. "Fire away. But we charge for consultations."

He sat by the fire, while I took a chair close to him.

"This person who has been getting into CP amp;L's computer," I said. "Do we know what else he has gotten into besides customer billing?" -f can't say we know everything," Lucy replied. "But the billing is a certainty, and customer info is in general."

"Meaning what?" Marino asked.

"Meaning that the information about customers includes billing addresses, phone numbers, special services, energyuse averaging, and some customers are part of a stocksharing program-". "Let's talk about stock sharing," I stopped her. "I'm involved in that program. Part of my check every month buys stock in CP amp;L, and therefore the company has some financial information on me, including my bank account and social security number." I paused, thinking. "Could that sort of thing be important to this hacker?"