"Of course not," I said. "You're a government agency. It's not your money, and you never have to show a profit."

Dr. Zollner smiled. "And the same in your business, sir."

"The very same. In any case, now we believe that the Gordons came to their senses, and, no longer satisfied with working in the interests of science for government wages, they discovered capitalism and went for the gold."

"Correct." He added, "You've spoken to their colleagues, you've seen what they did here, and now you can draw only one conclusion. Why are you still skeptical?"

"I'm not skeptical," I lied. Of course I was skeptical; I'm a New Yorker and a cop. But I didn't want to upset Dr. Zollner, Mr. Foster, or Mr. Nash, so I said, "I'm just trying to make sure the facts fit. The way I see it, either the Gordons' murders had nothing to do with their work here, and we're all following a false trail-or if their murders were related to their work, then most probably it had to do with the theft of a viral vaccine worth millions. Liquid gold. And it would appear that the Gordons were double-crossed, or maybe they tried to double-cross their partner, and were murdered-" Ping.

Jeez. There it was again. What…? It was out there. I couldn't see it, but I could hear its echo, and I could sense its presence, but what was it?

"Mr. Corey?"

"Huh?"

Dr. Zollner's twinkling blue eyes were appraising me through his little wire frame glasses. He said, "Is there something on your mind?"

"No. Oh, yeah. If I had to remove my watch, why can you keep your glasses?"

"That's the one exception. There is an eyeglass bath on the way out. Does this lead you to yet another clever thought or theory?"

"Gel sequencing plates disguised as eyeglasses."

He shook his head. "Idiotic. I think the gel plates were smuggled out in the lunch cart."

"Right."

Dr. Z looked at the clock on the wall and said, "Shall we continue?"

We all stood and deposited our plastic and paper in a red trash can lined with a red plastic bag.

Out in the corridor, Dr. Zollner said, "We will now enter Zone Three. There is a higher risk of contagion in Zone Three, of course, so if anyone does not want to go, I will have someone escort you back to the shower room."

Everyone seemed eager to burrow farther into the bowels of hell. Well, that might be overstating the response. Presently, we moved through a red door that was marked "Zone Three." Here, Zollner explained, his researchers worked with live pathogens-parasites, viruses, bacteria, fungi, and other yuckies-and he showed us a lab where a woman sat on a stool at a sort of opening in the wall. She had a mask on and her hands were covered with latex gloves. In front of her face was a plastic shield, something like a sneeze shield at a salad bar, but she wasn't handling cole slaw. Zollner said, "There is an exhaust in the opening where the pathogens are, so the risk of anything floating into the room is small."

Why," Max asked, "does she have a mask and we don't?"

"Good question," I agreed.

Zollner said, "She's much closer to the pathogen. If you want to get closer to take a look, I'll get you a mask."

"Pass," I said.

"Pass," everyone agreed.

Dr. Zollner moved closer to the woman and exchanged a few inaudible words with her. He turned, approached us, and said, "She's working on the virus that causes bluetongue disease." He thought a moment, then said, "Perhaps I got too close." He stuck out his tongue, which was actually bright blue, and looked down his nose. God in heaven… or is it the blueberry pie I had for lunch?" He laughed. We laughed. In truth, the gallows humor was wearing thin, even for me, and I have a lot of tolerance for stupid jokes.

We all left the room.

This part of the building looked less populated than Zone Two, and the people I saw looked a bit less jolly.

Zollner said, "There isn't much to see here, but if I say that, then Mr. Corey will insist on seeing every nook and cranny of the place."

"Oh, Dr. Zollner," I said, "have I given you cause to say such things about me?"

"Yes."

"Well, then, let's see every nook and cranny of the place."

I heard some groans, but Dr. Z said, "Very well, follow me." We spent the next half hour or so looking at nooks and crannies, and in truth, most of Zone Three looked the same-room after room of men and women peering through microscopes, making slides out of slime, slides from the blood and tissue of living and dead animals, and so on. Some of these people actually had their lunches with them and were eating while they played around with disgusting stuff.

We spoke to another dozen or so men and women who knew or worked with Tom and Judy, and while we were getting a more clear and more fully formed picture of their work, we didn't learn much new about their heads.

Still, I thought this was a useful exercise-I like to fix in my mind the milieu of the deceased, and later I usually think of something bright to follow up on. Sometimes, just casual chats with friends, family, and colleagues will turn up a word or two that can lead to the solution. Sometimes.

Zollner explained, "Most of these viruses and bacteria cannot cross the species barrier. You could drink a test-tube-ful of foot-and-mouth disease virus and not get much more than an upset stomach, though a cow would die from a quantity that would fit on the head or a pin.

"Why?"

"Why? Because the genetic makeup of a virus has to be able to… well, mesh with a cell to infect it. Human cells do not mesh with FMD virus."

Beth said, "But there's some evidence that Mad Cow Disease has infected humans."

"Anything is possible. That's why we're careful." He added, "Bugs bite."

Actually, bugs suck.

We went into another brightly lit room, and Zollner said, "In here we work with parasites. The worst is the screwworm. We've found a clever way to control this disease. We have discovered that the male and female screwworms only mate once in their lives, so we sterilize millions of the males with gamma rays and drop them by plane over Central America. When the male mates with the female, no offspring result. Clever, yes?"

I had to ask, "But is the female screwworm fulfilled?"

"She must be," Zollner replied. "She never mates again."

Beth offered, "There's another way to look at that."

Zollner laughed. "Yes. There is a female point of view there."

The persiflage finished, we all took turns looking at screwworm larvae under a microscope. Disgusting.

And on we went, into laboratories, and into rooms where horrible microbes and parasites were grown and stored, and into all sorts of weird places whose purposes and functions I only dimly understood. I kept in mind that my friends, Tom and Judy, walked these corridors and entered many of these rooms and labs every day. And yet, they seemed not to be depressed or anxious about any of it. At least not so I noticed.

Finally, Dr. Z said, "That's all of Zone Three. Now, once again I must ask you if you want to go farther. Zone Four is the most contaminated of all the zones, more so, actually, than Zone Five. In Five, you are always in a biohazard suit and respirator, and everything is decontaminated often. In fact, there is a separate shower for Zone Five. But Zone Four is where you will see the animal pens, the sick and dying animals, and also the incinerator and the necropsy rooms, if you wish. So, though we are clinically dealing here with animal diseases only, there may be other pathogens in the ambient environment. He added, "That means germs in the air."

Max asked, "Do we get face masks?"

"If you wish." He looked around and said, "All right. Follow me."

We approached yet another red door, this one marked "Zone rour, with the biohazard symbol. Some clown had stuck a particuarly gruesome skull-and-crossbones decal on the door-the skull was cracked and a snake slithered out of the crack and threaded itself through one of the skull's eye sockets. Also, a spider was crawling out of the grinning mouth. In fact, Dr. Zollner said, "I believe Torn is responsible for that horrible thing. The Gordons added some levity to this place."