Burton could not sleep. He lay in his bed on Level IV and stared at the ceiling, thinking. He could not get the image of that town out of his mind, or those bodies, lying in the street without bleeding . . .

Burton was not a hematologist, but his work had involved some blood studies. He knew that a variety of bacteria had effects on blood. His own research with staphylococcus, for example, had shown that this organism produced two enzymes that altered blood.

One was the so-called exotoxin, which destroyed skin and dissolved red cells. Another was a coagulase, which coated the bacteria with protein to inhibit destruction by white cells.

So it was possible that bacteria could alter blood. And it could do it many different ways: strep produced an enzyme, streptokinase, that dissolved coagulated plasma. Clostridia and pneumococci produced a variety of hemolysins that destroyed red cells. Malaria and amebae also destroyed red cells, by digesting them as food. Other parasites did the same thing.

So it was possible.

But it didn't help them in finding out how the Scoop organism worked.

Burton tried to recall the sequence for blood clotting. He remembered that it operated like a kind of waterfall: one enzyme was set off, and activated, which acted on a second enzyme, which acted on a third; the third on a fourth; and so on, down through twelve or thirteen steps, until finally blood clotted.

And vaguely he remembered the rest, the details: all the intermediate steps, the necessary enzymes, the metals, ions, local factors. It was horribly complex.

He shook his head and tried to sleep.

Leavitt, the clinical microbiologist, was thinking through the steps in isolation and identification of the causative organism. He had been over it before; he was one of the original founders of the group, one of the men who developed the Life Analysis Protocol. But now, on the verge of putting that plan into effect, he had doubts.

Two years before, sitting around after lunch, talking speculatively, it had all seemed wonderful. It had been an amusing intellectual game then, a kind of abstract test of wits. But now, faced with a real agent that caused real and bizarre death, he wondered whether all their plans would prove to be so effective and so complete as they once thought.

The first steps were simple enough. They would examine the capsule minutely and culture everything onto growth media. They would be hoping like hell to come up with an organism that they could work with, experiment on, and identify.

And after that, attempt to find out how it attacked. There was already the suggestion that it killed by clotting the blood; if that turned out to be the case, they had a good start, but if not, they might waste valuable time following it up.

The example of cholera came to mind. For centuries, men had known that cholera was a fatal disease, and that it caused severe diarrhea, sometimes producing as much as thirty quarts of fluid a day. Men knew this, but they somehow assumed that the lethal effects of the disease were unrelated to the diarrhea; they searched for something else: an antidote, a drug, a way to kill the organism. It was not until modern times that cholera was recognized as a disease that killed through dehydration primarily; if you could replace a victim's water losses rapidly, he would survive the infection without other drugs or treatment.