Doc could feel the tension in the village where GHQ was temporarily located long before they were close enough for details to register. The people were gathered in clusters, staring at the sky where the station must be. A few were pacing up and down, gesticulating with tight sweeps of their arms.

One woman suddenly went into even more violent action. She leaped into the air and then took off at a rapid trot, then a run. Her hands were tearing at her clothes and her mouth seemed to be working violently. She was halfway to the top of the nearest dune before a rifle cracked. She dropped, to twitch once and lie still.

Almost with her death, another figure leaped from one of the houses, his face bare of the necessary aspirator. He took off at a violent run, but he was falling from lack of air before the bullet ended his struggles.

The people suddenly began to move apart, as if trying to get away from each other. For weeks they had faced the horror with courage; now it was finally too much for them.

Tension mounted as no news came from the cities. Doc noticed that it seemed to aggravate or speed up the disease. He saw three men shot in the next half-hour.

He was trying to calm them with word of a possible cure for the plague, but their reactions were as curiously dull as those of Jake had been. As he spoke, they faced him with set expressions. At his mention of the need for the blood of young children, they turned from him, sullenly silent.

Jake came over, nodding unhappily. "It's what I was afraid might happen, Doc. George Lynn! Tell Doc what's wrong."

Lynn was reluctant, but he finally stumbled out his explanation. "It ain't like you, Doc. Comes from that Lobby woman you got. It's her dirty idea. We've seen the Lobby doctors cutting open our kids, poisoning their blood, and bleeding them dry. That ain't gonna happen again, Doc. You tell her it ain't!"

Doc swore as he realized their ignorance. An unexplained vaccination looked like poisoning of the blood. But he couldn't understand the bleeding part until Jake filled him in.

"Northport infant's wing. Each department has its own blood bank and donation is compulsory. Southport started it a couple months ago, too."

The long arm of the Lobby had reached out again. Now if he ever got them to try the treatment, it would be only after long sessions of preparing them with the facts, and there was hardly enough time for the crucial work!

By afternoon, Judge Ben Wilson reached them. His voice shook with fatigue as he climbed up to address the crowd through a power megaphone. "Southport's going crazy." He had to pause for breath between each sentence. "Earth's pulling back all the important people. They're packing them into the ships. They're leaving only colonials with no Earth rights. Those ships left when they decided the plague was coming from here. They won't let anybody back until the plague is licked. There won't be an Earth technician on Mars tomorrow."

"No bombs?" someone called.

"No bombs. The ships must have started before you rebelled, maybe meant honestly to save their own kind. But now it's a military action, and don't think it won't mean trouble. The poor devils in the city bet on the wrong horse. Now they can't run their food factories or anything else for long. Not without technicians. They've got to whip you now. Up to this time, they've been fighting for the Lobbies. Now they'll fight you for their own bellies to get your supplies. And they've still got shuttle rockets and fuel for them. Now beat it. I gotta confer with Jake."

Doc started after the judge, but Dr. Harkness caught his arm and drew him aside. Chris followed.

"I've found another epidemic," Harkness told them. "Over at Marconi. It's kept me on the run all night, and now half the village is down with it. Starts like a common cold, runs a fair fever, and the skin breaks out all over with bright red dots...."

He went on describing it. Chris began asking him about what medical supplies he had brought with him, pilfered from Northport hospital. She seemed to know what it was, but refused to say until she saw the cases. Doc also preferred to wait. Sometimes things weren't as bad as they seemed, though usually they were worse.

Marconi was dead to all outward appearances, with nobody on the streets. It had been a village of great hopes a week before, since this was where they had decided to experiment with switching the people back to Earth-normal. They'd had the best chance of survival of anyone on Mars until this came up.

Three people lay on the beds in the first house Harkness led them to. The room was darkened, and a man was stumbling around, trying to tend the others, though the little spots showed on his skin. He grinned weakly. "Hi, Doc. I guess we're making a lot of trouble, ain't we?"

Chris gave Doc no chance to answer. "Just as I thought. Measles! Plain old-fashioned measles."

"Figured so," the sick man said. "Like my brother back on Earth."

The others looked doubtful, but Doc reassured them. Chris should know; she'd worked in a swanky hospital where the patients were mostly Earth-normal. Measles was one of the diseases which was foiled by the metabolism switch. Well, at least they wouldn't have to be quarantined here.

Chris finished treating the family with impersonal efficiency, discussing the symptoms loudly with Harkness. "It's a good thing it isn't serious!"

"No," Harkness answered bitterly. "Not serious. It's only killed five children and three adults so far!"

"It would, here," Doc agreed unhappily. He led Chris out of the room on the pretext of washing his hands. "It's serious enough to force us to abandon the whole idea of going back to Earth-normal. Measles today, smallpox, tuberculosis, scarlet fever and everything else tomorrow. These people have lived Mars-normal so long their natural immunity has been destroyed. On Earth where the disease was everywhere, kids used to pick up some immunity with constant exposure, even without what might be called a case of the disease. Here, the blood has no reason to build antibodies. They can be killed by things people used to laugh at. How the disease got here, I don't know. But it's here. So we'll have to give up the idea of switching back to Earth-normal."

He gathered up one of the kits and started toward the other houses. "And Lord knows how long it will take to get the blood for the other treatment, even if it works."

They worked as a team for a while, with Harkness frowning as he watched Chris. Finally the young doctor stopped Chris outside the fifth house. "These are my patients, Dr. Ryan. I left the Lobby because I didn't believe colonials were mere livestock. I still feel the same. I appreciate your help in diagnosis and methods of treatment. But I can't let you handle my patients this way."

"Dan!" She swung around with eyes glazing. "Dan, are you going to stand for that?"

"I think you'd better wait in the tractor, Chris."

He was lucky enough to catch the kit she threw at him before its precious contents spilled. But it wasn't luck that guided his hand to the back of her skirt hard enough to leave it stinging.

Her face froze and she stormed out. A moment later they heard the tractor start off.

But Doc had no time to think of her. He and Harkness split up and began covering the streets, house by house, while he passed on the word to abandon the metabolism switch and go back to Mars-normal.

Jake sent two other doctors to relieve them late in the evening. Things were somewhat quieter at GHQ as Doc reported the events at Marconi.

"Where's Dr. Ryan?" Jake asked at last.

Doc exchanged glances with Harkness. "She isn't in the lab?"

"Wasn't there an hour ago."

Doc cursed himself for letting her go. With the knowledge that the radio in the mike was disabled, she'd obviously grabbed the first chance to report back. And with her had gone news of the only cure they had found.

Jake took it as philosophically as he could, though it was a heavy blow to his hopes. They spent half the night looking for her tractor, on the chance that she might have gotten lost or broken down, but there was no sign of it.

She was waiting in the laboratory when he returned at dawn. Her face was dirty and her uniform was a mess. But she was smiling. She got up to greet him, holding out two large bottles.

"Infant plasma—straight from Southport. And if you think I had it easy lying my way in and out of the hospital, you're a fool, Dan Feldman. If the man who took my place there hadn't been a native idiot, I never would have gotten away with it."

The things he had suspected could still be right, he realized. She could have reported everything to the Lobby. It was a better explanation than her vague account of bullying her way in and out. But she'd had a rough drive, and he wanted the plasma. Curiously, he was glad to have her back with him. He reached out a hand for the bottles.

She put the bottle on the table and grabbed up a short-bladed knife. "Not so fast," she cried. Her eyes were blazing now. "Dan Feldman, if you touch those bottles until you've crawled across the floor on your face and apologized for the way you treated me the last few days, I'll cut your damned heart out."

He shook his head, chuckling at the picture she made. There were times when he could almost see why he'd married her.

"All right, Chris," he gave in. "I'll be darned if I'll crawl, but you've earned an apology. Okay?"

She sighed uncertainly. Then she nodded and began changing for work.