“Dr. Navarre’s misfortune was that in studying what makes brain cells grow, he also had to study what kills them. One of the amazing things about the human body, you see, is that during the first years of life it must kill roughly half the brain cells it’s born with. A similar process can be stimulated in adult brains by something called ‘tumor necrosis factor,’ or TNF. Unfortunately, some of Dr. Navarre’s colleagues at Unetat realized that the same chaperone he was using to escort the good stuff—the neurotrophins—could be used to introduce the bad stuff. Once the TNF is inside the brain, it activates what we call ‘suicide genes.’ They make proteins that trigger a lethal cascade of events—a programmed, regulated destruction of brain cells—known as apoptosis. Scientists give these genes names like ‘grim,’ and ‘reaper.’ I suppose they enjoy jokes like that.”

“What does this brain death look like, when it happens?” I asked.

“It’s quite horrible. It’s like the dementia people suffer in the final stages of AIDS, but worse. Disorientation, acute anxiety, loss of control of all bodily functions. It’s as if the brain and spinal cord were melting away. There’s nothing left. The victims die utterly alone, in pure terror.”

Her explanation was careful and specific, spoken in the measured tones of a scientist. I tried to imagine thousands of people suffering in that way, unattended by doctors; to imagine children, terrified, as they watched their parents die. Nuclear war would be far preferable. “How would this weapon be delivered?” I asked.

“That’s the hardest part. We think the Chinese are focusing on delivery systems. The most likely way would be to insert this TNF and its prion chaperone into a virus that is airborne, like Hanta virus. A missile warhead would release the virus in the air, over the target population. People who inhaled the virus would become infected, and many of them would die. The useful thing about Hanta virus for weapons designers is that it can survive in the soil for a very long time. Every dry and windy day, it would spread farther and infect more people.”

She spoke so crisply, so bloodlessly. I didn’t want to hear any more about how it would work. I wanted to know how it could be stopped.

“What if Dr. Navarre leaves China,” I said, “will that end the research?”

“No, but they will have great difficulty without him. He is the only one who fully understands the biological science. He is like an Oppenheimer or a Teller. They need him.”

She switched the lights back on. She looked more substantial now than before, as if she had been bolstered by her own presentation.