Free Final Reckoning: The Fate of Bester by J. Gregory Keyes Page A

plague.
    In actual fact, he was a sort of alchemist-inquisitor, someone who could drag the secret out of any compound he was given, no matter how strange or complex. So Garibaldi didn’t really care if the guy knew anything about living it up.
    “It’s choline ribosylase. It controls the production of certain irregular neurotransmitters.”
    “Which means what? In English? In plain English.”
    “How much do you know about neurons?”
    “Sixth-grade stuff”
    “Hmm… Well, nerves are often compared to wiring, or to some other linear, conductive system. It’s a bad analogy, on any number of levels. The nervous system-the brain, the spinal cord, sensory and motor nerves-are all composed of specialized cells called neurons. But neurons, strictly speaking, don’t act as conductors. They act as generators, in a sense. each one producing its own electrical pulses.”
    “So far I’m with you.”
    Drennan’s face said I should hope so, but he held his tongue.
    “A neuron has a sort of branching tree of dendrites that almost connect it to other nerve cells - I’ll get to that in a moment. Each one also has a longer appendage called an axon. When an electrical pulse is generated by the neuron, it flows down the axon until it comes to the next neuron-or, rather, to the gap separating it from the next neuron, the synapse.”
    “And the pulse jumps the gap or not, right?”
    “Not exactly. The impulse itself doesn’t cross the space. When the impulse reaches the end of the axon, it triggers small packets, telling them to release a combination of neurotransmitters. These are complex chemical compounds that float across the intervening space and tell the neuron next door what to do-whether to generate its own electrical pulse or not. There are upwards of fifty kinds of neurotransmitters in most people. They’re triggered by different sorts of impulses, and in turn cause neighboring neurons to react in different ways. When these neurotransmitters malfunction, especially when they are underproduced, they cause neurological problems. Alzheimer’s, for instance, involves among other things the underproduction of a neurotransmitter.
    Certain kinds of messages can’t be carried from one neuron to another because there is no messenger that will do so. Most psychotropic drugs mimic neurotransmitters in some way, causing neurons to react to stimuli that don’t really exist.”
    “So these are irregular neurotransmitters?”
    “There’s a long list of them, but I imagine you’re interested in the case at hand. There is a rare condition involving a viruslike organism that mimics glial cells-the cells that maintain the biochemical functions of the brain. Imagine them also as the packing pellets that support the fibrous, fragile neurons. Given time, these mutant cells can subvert and replace all of the brain’s natural glial cells. What’s interesting is that in most cases, this process is harmless, as the invasive cells perfectly mimic those they replace. They have latent genetic machinery that makes them different, but it isn’t ever activated. In a minority of cases, however, they stimulate the production of certain neurotransmitters that don’t occur naturally in the human body. This scenario is limited to telepathic individuals, and…”
    “Hold it right there. Telepaths?”
    “Yes.”
    “Why?”
    “We don’t know. We still don’t know exactly how telepathy works. Telepaths have quirky glial cells anyway, and we’ve never quite hammered out the link.”
    “Okay. So this is a disease, right? A virus?”
    “Not exactly a virus, but it’s not a bad analogy either.”
    “Natural?”
    “Good question. We don’t really think so. The imitative cells are too, um, well-designed, so to speak.”
    “What does it do, this disease?”
    “At first, nothing. There actually seems to be some enhancement of telepathic abilities-or more specifically, of the processing of telepathic information and impulses. It speeds it