Dr. Feldman leaned back from his microscope and lighted another bracky weed. He glanced about the room and sighed wearily. Maybe he'd been better off when he had no friends and couldn't risk the safety of others in an effort to do research that was the highest crime on two worlds.

The evidence of his work was hidden thirty feet beyond his former laboratory in Jake's village, with a tunnel that led from another root-cellar. The theory was the old one that the best place to avoid discovery was where you had already been discovered. If their spies had identified his former hangout, they'd never expect to have him set up research nearby. It was a nice theory, but he wasn't sure of it.

Jake looked up from a cot where he'd been watching the improvised culture incubator. "Stop tearing yourself to bits, Doc. We know the danger and we're still darned glad to have you here working on this."

"I'm trying to put myself together into a whole man," Doc told him. "But I seem to come out wholly a fool."

"Yeah, sure. Sometimes it takes a fool to get things done; wise men wait too long for the right time. How's the bug hunt?"

Doc grunted in disgust and swung back to the microscope. Then he gave up as his tired eyes refused to focus. "Why don't you people revolt?"

"They tried it twice. But they were just a bunch of pariahs shipped here to live in peonage. They couldn't do much. The first time Earth cut off shipments and starved them. Next time the villages had the answer to that but the cities had to fight for Earth or starve, so they whipped us. And there's always the threat that Earth could send over unmanned war rockets loaded with fissionables."

"So it's hopeless?"

"So nothing! The Lobbies are poisoning themselves, like cutting off Medical service until they cut themselves out of a job. It's just a matter of time. Go back to the bugs, Doc."

Doc sighed and reached for his notes. "I wish I knew more Martian history. I've been wondering whether this bug may not have been what killed off the old Martians. Something had to do it, the way they disappeared. I wish I knew enough to make an investigation of those ruins out there."

"Durwood!" Jake had propped himself on an elbow, staring at Doc in surprise.

Doc scowled. "Clive Durwood, you mean? The archeologist who dug up what little we know about the ruins?"

"Yeah, before he went back to Earth and started living off his lectures. He came here again three years ago and dropped dead in Edison on the way to some other ruins. Heart failure, they called it, though it was more like the two old farmers who ran themselves to death last month. I saw him when they buried him. His face looked funny, and I think he had those little specks, though I may remember wrong." He grimaced. "Mars is tough, Doc; it has to be. Some of the plant seeds Durwood found in the ruins grew! Maybe your bugs waited a million years till we came along."

"What about the farmers? Did they meet Durwood?"

Jake nodded. "Must have. He lived in their village most of the time."

Doc went through his notes. He'd asked for reports on all deaths, and he finally found the account. The two old men had been nervous and fidgety for weeks. They were twins, living by themselves, and nobody paid much attention. Then one morning both were seen running wildly in circles. The village managed to tie them up, but they died of exhaustion shortly after.

It wasn't a pretty picture. The disease might have an incubation period of nearly fifteen years, judging by the length of time it had taken to hit Durwood. It must spread from person to person during an early contagious stage, leaving widening circles behind Durwood and those first infected. When matured, any other sickness would set it off, with few symptoms of its own. But without help, it still killed its victims, apparently driving them madly toward frenzied physical effort.

He studied the culture on a slide again. He'd tried Koch's method to get a pure strain, splattering the bugs onto a native starchy root and plucking off individual colonies. About twenty specimens had been treated with every chemical he could find. So far he'd found a few things that seemed to stop their growth, but nothing that killed them, except stuff far too harsh to use in living tissue.

He had nearly forty cases of deaths that showed symptoms now, and he went back over them, looking for anything in common that went back ten to twenty years before death. There were no rashes nor blisters. A few had had apparent colds, but such were too common to mean anything.

Only one thing appeared, about fourteen years before their deaths. The people interviewed about the victims might be vague about most things, but they remembered the time when "Jim had the jumping headache."

"Jake," Doc called, "what's jumping headache? Most people seem to have it some time or other, but I haven't run across a case of it."

"Sure you have, Doc. Mamie Brander's little girl a few weeks ago. Feels like your pulse is going to rip your skull off, right here. Can't eat because chewing drives you crazy. Back of your head, neck and shoulders swell up for about a week. Then it goes away."

Then it goes away—for fourteen years, until it comes back to kill!

Doc stared at his charts in sudden horror. It was a new disease—thought to be some virus, but not considered dangerous. Selznik's migraine, according to medical usage; you treated it with hot pads and anodyne, and it went away easily enough.

He'd seen hundreds of such cases on Earth. There must be millions who had been hit by it. The patent-medicine branch of the Lobby had even brought out something called Nograine to use for self-treatment.

"Something important?" Jake wanted to know.

Feldman nodded. "How much weight do you swing in other villages, Jake?"

"People sort of do me favors when I ask," Jake admitted. "Like swiping those medical journals from Northport for you, or like Molly Badger getting that job as maid to spy on Chris Ryan. Name it and I'll do my best."

Doc had a vague idea of village politics, but he had more important things to think of. Most of his foul mood had disappeared with the clue he'd stumbled on, and his chief worry now was to clinch the facts.

Feldman considered the problem. "I want a report on every case of jumping headache in every village—who had it, when, and how old they were. This place first, but every village you can reach. And I'll want someone to take a letter to Chris Ryan."

Jake frowned at that, but went out to issue instructions. Doc sat down at a battered old typewriter. Writing Chris might do no good, but some warning had to be gotten through to Earth, where the vast resources of Medical Lobby could be thrown into the task of finding the cause and cure of the disease. The connection with Selznik's migraine had to be reported. If something could blast the Lobby into action, it wouldn't matter quite so much what they did to him. He wasn't foolish enough to expect gratitude from them, but he was getting used to the idea that his days were numbered. The plague was more important than what happened to him.

The letter had been dispatched by the time Jake returned. "Here's the dope for this village. Everybody accounted for except you."

"Never had it, Jake." Feldman went down the list. "Most of it fourteen years ago. That fits. About the only exceptions are the kids who seem to get it between the ages of two and three. Eighty-seven out of ninety-one!"

He stared at the figures sickly. Most of the village not only had the plague but must be near the end of the incubation period. It looked as if most of the village would be dead before another year passed.

"Bad?" Jake asked.

"The first symptom of Martian fever."

The old man whistled, the lines around his eyes tightening. "Must be me," he decided. "I'm the guy who must have brought it here, then. I used to spend a lot of time with Durwood at his diggings!"

There was a constant commotion all that day and the next as runners went out to the villages and came back with reports. The variation from village to village was only slight. Most of Mars seemed to have advanced cases of Martian fever.

Without animals for investigation and study, real research was difficult. Doc also needed an electron microscope. He was reasonably sure that the disease must travel through the nerves, but he had found no proof beyond the hard lump at the base of the neck. There it was a fair-sized organism. Elsewhere he could find nothing, until the black specks developed.

His eyes ached from trying to see more than was visible in the microscope. The tantalizing suggestions of filaments around the nuclei might be the form of plague that was contagious. They might even be the true form of the bug, with the bigger cell only a transition stage. There were a number of diseases that involved complicated changes in the organisms that caused them. But he couldn't be sure.

He finally buried his head in his hands, trying to do by pure thought what he couldn't do in any other way. And even there, he lacked training. He was a doctor, not a xenobiologist. Research training had been taboo in school, except for a favored few.

The reports continued to come in, confirming the danger. They seemed to have the worst plague on their hands in all human history; and nobody who could do anything about it even knew of it.

"Molly reports that your letter got some results," Jake reported. "Chris Ryan brought home one of the electron microscopes and a bunch of equipment from the hospital pathology room. Think she'll get anywhere?"

Doc doubted it. Damn it, he hadn't meant for her to try it, though she might have authority for routine experiments. But it was like her to refuse to pass on the word without trying to prove her own suspicion of him first.

He tried to comfort himself with the fact that some men were immune, or seemed so; about three out of a hundred showed no signs. If that immunity was hereditary, it might save the race. If not....

Jake came in at twilight with a grim face. "More news from Molly. The Lobby is starting out to comb every village with a fault-finder, starting here. And this hole will show up like a sore thumb. Better start packing. We gotta be out of here in less than an hour!"