Could it be radiation poisoning? Something so subtle that the dosage meters aren’t equipped to detect it? After all, everyone else has been outside the dome much more than I have. I’ve stayed in here while they’ve been out doing their work.

That couldn’t be it. There’s no strange radiation on Mars. Naguib and the others have been measuring the radiation environment since we landed. And the unmanned probes were measuring it for years before we arrived here.

Still the unconscious thought pecked at him. Something about the vitamins.

Reed closed his eyes and envisioned his morning routine. He came to the infirmary and took his own vitamin pills, then went to the galley and made certain that there were enough there for all the others and that they took theirs with their breakfasts. He no longer mixed his morning cocktail; he wanted his head absolutely clear of drugs during this emergency. He personally watched everyone swallow their pills each morning, except for the occasional early bird who finished breakfast before he got to the galley. Since this malady had struck, there had been no one up and stirring earlier than Tony, not even Vosnesensky.

His eyes suddenly shot to the cabinet where the vitamin bottles stood. Each bottle held five hundred of the ovoid orange pills.

And locked in his medicine chest was a smaller bottle, the one he took his own pills from.

"Oh no," he groaned.

Yang jerked from her self-absorbed study as if Reed had slapped her. "What? What did you say?"

"I don’t take my vitamin pills from the same jar as the others."

She looked hard at him. "Does that make a difference?"

"It shouldn’t… except—"

Yang Meilin watched him expectantly. Tony could feel the anticipation radiating from her tense body.

"That first jar there," he pointed to the glass-fronted cabinet, "was open when the meteor strike punctured the dome. The other jars have never been opened; they’re still in their original seals."

Tony felt his face flush deeply with guilt. When the meteoroid had punctured the dome and all the alarms had gone off, that one big jar had been sitting open on his desk. He had knocked the bottle over in his rush to get out of the infirmary and into his hard suit. Afterward, when the emergency was over, he had picked up the pills scattered across his desktop and replaced them in the same bottle, discarding only those he had found on the floor.

Nothing wrong with them, he had told himself. Then he had transferred the pills to the smaller bottles that fit into the galley shelves.

His own supply of vitamin supplement was already in a smaller bottle, safely sealed in his medicine cabinet along with his amphetamines and other drugs. That medicine cabinet was not only locked; it was airtight.

"Their pills were exposed to pure oxygen," he muttered.

Yang put a hand to her lips.

"Yes," Reed said, putting the scenario together as he spoke, "the dome was pressurized with pure oxygen for almost thirty-six hours. It took a couple of days before we pulled enough nitrogen from the air outside to make an Earth-normal mixture in here again."

"Pure oxygen…"

"Pure oxygen will destroy ascorbic acid," Reed said absently, as if recalling some obscure test question from a college examination.

"The pills they are taking have no vitamin C in them."

"Right. They’ve all come down with scurvy."

"Scurvy!" Yang immediately grabbed the computer keyboard and typed furiously for a few moments. The machine hummed to itself, while Tony writhed inwardly in mental agony. My fault. Every bit of it is my own stupid fault.

"It correlates," Yang said, eyeing the new data displayed on the computer screen. "They all show the symptoms of scurvy."

Reed sat back in his chair feeling as weak and hollow as if he had come down with the affliction himself. Scurvy. And it’s all my fault. If only I had seen it earlier. Of course it had to be that. The oxygen, the pills…

He looked up and saw that Yang was striding through the infirmary doorway.

"Where are you going?" Tony called to her as he scrambled from behind his desk.

"Wardroom," she answered over her shoulder. Little though she was she marched like a trained soldier, arms swinging, boots clacking on the plastic floor. Tony hurried to catch up with her.

"Looking for anyone in particular?" he asked.

"The ground team leader. Vosnesensky."

"Ah. Yes, of course."

"You have bottles of vitamins that have not been unsealed?" Yang asked. "Not contaminated by oxygen?"

"Yes," he answered. "Fifteen hundred of them, in three sealed bottles."

Monique Bonnet was at the wardroom table with Paul Abell and Mironov, all three of them slumped wearily.

"Where is the group leader?" Yang asked.

Monique gave an exhausted sigh, then replied, "I believe he is at the communications console."

Yang headed off for the comm console without another word, Reed trailing right behind her. She must be hell on wheels in a hospital, the Englishman thought. God help the man or woman who gets in her way!

Vosnesensky looked as if he were ready to drop off to sleep. He sagged in the chair; his face looked puffy, red eyed, bleary. Connors’s black features in the communications screen looked no better; worse, in fact.

"I require your cooperation," Yang said without preamble.

Vosnesensky turned in his chair, started to push himself to his feet, then gave it up and simply sat there looking at the Chinese physician, almost eye to eye.

"You must begin taking large doses of vitamins, now, immediately."

"Vitamins?" Vosnesensky was saying dully. "But we take vitamins. We take them every day, on the regular schedule."

"They are contaminated," Yang said.

Vosnesensky’s eyes shifted to Reed.

"It’s true, Mikhail Andreivitch," said Tony. "They were bathed in oxygen after the meteor hit. They’re practically useless."

"But what has that to do…?"

"Scurvy," said Yang.

"Scurvy?"

"That’s right," Reed said. "You’ve all come down with scurvy from lack of vitamin C."

Silently he added, Because of me. Because I panicked. Because I didn’t want to see the truth. I’m a murderer. That’s what I am.

"Vitamin deficiency?"

The words woke Jamie. He had been sleeping dreamlessly when Connors’s voice, shrilly high-pitched, cut through to his conscious mind.

Untangling himself from the thin blanket, Jamie slithered out of his bunk and padded in his stockinged feet forward to the cockpit. The rover felt shivering cold. Connors was talking to Vosnesensky. Both men looked utterly drained, but there was a strange grin on the Russian’s image on the screen.

"We have scurvy," Vosnesensky said, almost as if it were a joke.

"Scurvy?"

"It is definite. Yang’s tests were analyzed during the night. Our vitamin pills have been poisoned — no, that is not the correct word. The vitamin C in the pills has been deactivated because it was exposed to oxygen after the meteorite hit. Without sufficient vitamin C we have all come down with scurvy."

Jamie slumped into the right-hand seat. "You mean like old-time sailors who’ve been at sea too long?"

"That’s why they called the Brits ‘limeys,’" Connors said, his voice still echoing disbelief. "Because they carried limes and other fresh fruits aboard their ships once they figured out what caused scurvy."

"Scurvy," Jamie mumbled. "Scurvy."

"According to Dr. Yang it will take several days before the symptoms go away," Vosnesensky said.

"What about us?" Connors asked.

The Russian’s grin disappeared like a light winking off. "So far, Kaliningrad has forbidden a rescue flight from orbit. Not until they make a decision."

"We’re stuck here until they make up their minds?" Connors said it as if it were equivalent to a death sentence.