Three days later, Doc saw his first runner.

The tractor was churning through the sand just before sundown, heading toward another one-night stand at a new village. Lou was driving, while Doc and Jake brooded silently in the back, paying no attention to the colors that were blazoned over the dunes. The cat-and-mouse game was getting to Doc. There was no real assurance that the village they were approaching might not be the target the Lobby had chosen for the next investigation.

Lou braked the tractor to a sudden halt, and pointed.

A figure was running frantically over one of the low dunes with the little red sun behind him. He seemed headed toward them, but as he drew nearer they could see that he had no definite direction. He simply ran, pumping his legs frantically as if all the devils of hell were after him. His body swayed from side to side in exhaustion, but his arms and legs pumped on.

"Stop him!" Jake ordered, and Lou swung the tractor. It halted squarely in the runner's path, and the figure struck against it and toppled.

The legs went on pumping, digging into the dirt and gravel, but the man was too far gone to rise. Jake and Lou shoved him through the doors into the tractor and Doc yanked off his aspirator.

The man was giving vent to a kind of ululating cry, weakened now almost to a whine that rose and fell with the motion of his legs. Sweat had once streaked his haggard face, but it was dry and blanched to a pasty gray.

Doc injected enough narcotic to quiet a maddened bull. It had no effect, except to upset the rhythm of the arms and legs. It took five more minutes for the man to die.

The specks were larger this time—the size of periods in twelve-point type. The lump at the base of the skull was as big as a small hen's egg.

"From Edison, like the others so far. Jack Kooley," Jake answered Doc's question. "Durwood spent a lot of time here on his first expedition, so it's getting the worst of it."

Doc pulled the aspirator mask back over the man's face and they carried him out and laid him on a low dune. They couldn't risk returning the corpse to its people.

This was only the primary circle of infection, direct from Durwood. The second circle could be ten times as large, as the infection spread from one to a few to many. So far it was localized. But it wouldn't stay that way.

Doc climbed slowly out of the tractor, lugging his small supplies of equipment, while Jake made arrangements for them to spend the night in a deserted house. But the figure of the runner and his own failures to find more about the disease kept haunting Doc. He began setting up his equipment grimly.

"Better get some sleep," Jake suggested. "You're a mite more tired than you think. Anyhow, I thought you told me you couldn't do any more with what you've got."

Feldman looked at the supplies he had spread out, and shook his head wearily. He'd been over every chemical and combination a dozen times, without results that showed in the limited magnification of the optical mike.

He snapped the case shut and hit the rude table with the heel of his hand. "There are other supplies. Jake, do you have any signal to get in touch with Molly at the Ryan house?"

"Three raps on the rear left window. I'll get Lou."

"No!" Doc came to his feet, reaching for his jacket. "They're looking for three men now. It's safer if I go alone—and I'm the only one who knows what supplies are needed. With luck, I may even get the electron mike. Got a gun I can borrow?"

Jake found one somewhere, an old revolver with a few loads. He began protesting, but Doc overruled him sharply. Three men could no more fight off the police than one, if they were spotted. He swung toward the tractor.

"You'd better start spreading the word on everything we know. If people realize they're already safe or doomed it'll be better than having them going crazy to avoid contagion."

"Most of the villages know already," Jake told him. "And damn it, get back here, Doc. If you can't make it, turn tail quick, and we'll think of something else."

Southport seemed normal enough as Doc drove through its streets. The stereo house was open, and the little shops were brightly lighted. He stopped once to pull a copy of Southport's little newspaper from a dispenser. All was quiet on its front page, too.

As usual, though, the facts were buried inside. The editorial was pouring too much oil on the waters in its lauding of the role of Medical Lobby on Mars for no apparent reason. The death notices no longer listed the cause of death. Medical knew something was up, at least, and was worried.

He parked the tractor behind Chris' house and slipped to the proper window. Everything was seemingly quiet there. At his knock, the shade was drawn back, and he caught a brief glimpse of Molly looking out. A moment later she opened the rear lock to let him into the kitchen.

"Shh. She's still up, I think. What can I do, Doc?"

He tried to smile at her. "Hide me until it's safe to get into her laboratory. I've got to—"

The inner kitchen was kicked open and Chris stood beyond it, holding a cocked gun in her hand.

"It took longer than I expected, Dan," she said quietly. "But after your letter, I knew you'd swallow the bait. You bloody fool! Did you really believe I'd start doing research here just because of your imaginings?"

He slumped slowly back against the sink. "So this is a fool's errand, then? There never was any equipment here?"

"The equipment's here—in my office. I guessed your spies would report it, so it had to be here. But it won't help you now, pariah Feldman!"

He came from his braced position against the sink like a spring uncoiling. He expected her to shoot, but hoped the surprise would ruin her aim. Then it was too late, and his boot hit the gun savagely, knocking it from her hand. Life in the villages had hardened him surprisingly. She was comparatively helpless in his hands. A few minutes later, he had her bound securely with surgical tape Molly brought him. She raged furiously in the chair where he'd dumped her, then gave up.

"They'll get you, Daniel Feldman!" Surprisingly, there was no rage in her voice now. "You won't get away from us. The planet isn't big enough."

"I got away from your trial," he reminded her. "And I got away and lived when you left me without a chance on the ground of the spaceport."

She laughed harshly. "You got away then? You fool, who do you think gave you the extra battery so you could live long enough to be helped at the spaceport? Who hired a fool like Matthews so you wouldn't get the death sentence you deserved? Who let you get away as an herb doctor for months before you set yourself up as God and a traitor to mankind again?"

It shook him, as it was probably intended to do. How had she known about the extra battery? He'd always assumed that Ben had returned to give it to him. But in that case, Chris couldn't know of it. Then he hardened himself again. In the old days, she'd always had one trump card he couldn't beat and hadn't expected. But too much was involved for games now.

"Any police around, Molly?" he asked.

Molly came back a minute later to report that everything looked clear and to show him where the equipment had been set up in Chris' office. It was all there, including the electron mike—a beautiful little portable model. There was even a small incubator with its own heat source into which he immediately transferred the little bottles he'd been keeping warm against his skin. Most of the equipment had never been unpacked, which made loading it onto his tractor ridiculously easy.

"Better come with me now, Molly," he suggested at last. Then he turned to Chris, who was watching him with almost no expression. "You can wriggle your chair to the phone in half an hour, I guess. Knock the phone off and yell for help. It's better than you deserve, unless you really did leave me that battery."

"You won't get away with it," she told him again, calmly this time.

"No," he admitted. "Probably not. But maybe the human race will, if I have time to find an answer to the plague you won't see under your nose. But you won't get away with it, either. In the long run, your kind never do."

Molly was sniffling as they drove away. It had probably been the best life she'd known, Doc supposed. Chris could be kind to menials. But now Molly's work was done, and she'd have to disappear into the villages. He let her off at the first village and drove on alone. He was itching to get to the microscope now, hardly able to wait through the long journey back to Jake. His impatience grew with each mile.

Finally he gave up. He swung the tractor into a small gulley between sand dunes, left the motor idling and pulled down the shades the villagers used for blackout traveling. There was power enough for the mike here, and the cab was big enough for what he had to do.

He mounted the mike on the tractor seat and began laying out the collection of smears and cultures he had brought. It had been years since he'd made a film for the electron mike, but he found it all came back to him as he worked.

His hands were sweating with tension as he inserted the first film into the chamber. He had the magnetic "lenses" set for twenty thousand power, but a quick glance showed it was too weak. He raised the power to fifty thousand.

The filaments were there, clear and distinct.

He turned on the little tape recorder that had been part of Chris' equipment and set the microphone where he could dictate into it without stopping to make clumsy notes. He readjusted the focus carefully, carrying on a running commentary.

Then he gasped. Each of the little filaments carried three tiny darker sections; each was a cell, complete in itself, with the typical Martian triple nucleus.

He put a film with a tiny section of the nerve tissue from a corpse into the chamber next, and again a quick glance at the screen was enough. The filaments were there, thickly crowded among nerve cells. They did travel along the nerves to reach the base of the brain before the larger lump could form.

A specimen from one of the black specks was even more interesting. The filaments were there, but some were changed or changing into tiny, round cells, also with the triple dark spots of nuclei. Those must be the final form that was released to infect others. Probably at first these multiplied directly in epithelial tissue, so that there was a rapid contagion of infection. Eventually, they must form the filaments that invaded the nerves and caused the brief bodily reaction that was Selznik's migraine. Then the body adapted to them and they began to incubate slowly, developing into the large cells he had first seen. When "ripe", the big cells broke apart into millions of the tiny round ones that went back to the nerve endings, causing the black spots and killing the host.

He knew his enemy now, at least.

He reached for the controls, increasing the magnification. He would lose resolution, but he might find something more at the extreme limits of the mike.

Something wet and cold gushed into his face. He jerked back, trying to wipe it off, but it was already evaporating, and there was a thick, acrid odor in the cab. He grabbed for his aspirator, then tried to reach the airlock. But paralysis was already spreading through him, and he toppled to the floor before he could escape.

When he came to, it was morning outside, and Chris was waiting inside the cab with two big Lobby policemen. A hypo in her hand must have been what revived him.

She touched the electron microscope with something like affection. "The Lobby technicians did a good job on this, don't you think, Dan? I warned you, but you wouldn't listen. And now we've even got your own taped words to prove you were doing forbidden research. Fool!"

She shook her head pityingly as the tractor began moving with two others toward Southport.

"You and your phony diseases. A little skin disorder, Selznik's migraine, and a few cases of psychosis to make a new disease. Do you think Medical Lobby can't check on such simple things? Or didn't you expect us to hear of your open talk of revolt and realize you were planning to create some new germ to wipe out the Earth forces. Maybe those runners of yours were real, mass murderer!"

She drew out another hypo and shoved the needle into his arm. Necrosynth—enough to keep him unconscious for twenty-four hours. He started to curse her, but the drug acted before he could complete the thought.