After two weeks of flight through the vast blackness of interstellar s.p.a.ce, the _Lord Nelson_ came out of overdrive and set itself in an orbit around Fomalhaut V. Lieutenant Jervis, the sole survivor of the ill-fated _Mavis_, located the small valley between the giant crags that covered the planet, and the huge spherical bulk of the s.p.a.ceship settled gently to the floor of the valley.

They were gathered in the central room of the ship ten minutes after the _all-clear_ rang through the corridors, informing everyone that the landing had been safely accomplished. From the portholes they could see the white bones of the _Mavis's_ crew lying on the reddish sand of the valley bottom.

"There they are," Jervis said quietly. "Just bones. Those were my shipmates."

Wayne saw Sherri repress a shudder. Little heaps of bones lay here and there on the sand, shining brightly in the hot sun. That was the crew of the _Mavis_--or what was left of them.

Colonel Petersen entered the room and confronted the crew. "We're here,"

he said. "You know the schedule from now on. No one's to leave the ship until we've made a check outside, and after that--a.s.suming it's OK to go out--no more than six are to leave the ship at any one time."

He pointed to a row of metal magnetic tabs clinging to the wall nearest the corridor that led to the airlock. "When you go out, take one of those tabs and touch it on your suit. There are exactly six tabs. If none are there, don't go out. It's as simple as that."

Four men in s.p.a.cesuits entered the room, followed by two others. The leader of the group saluted. "We're ready, sir," he said.

"Go out and get a look at the bodies," the colonel told the men, who were Medical Corpsmen. "You know the procedure. Air and sand samples too, of course."

The leader saluted again, turned, and left. Wayne watched the six s.p.a.cesuited figures step one at a time to the wall, withdraw one of the metal tabs, and affix it to the outer skin of his suit. Then they went outside.

Captain Wayne and Sherri James stood by one of the portholes and watched the six medics as they bent over the corpses outside. "I don't get it, I just don't understand," Wayne said quietly.

"What don't you get?" Sherri asked.

"Those skeletons. Those men have only been dead for two months, and they've been reduced to nothing but bones already. Even the fabric of their clothing is gone. Why? There must be something here that causes human flesh to deteriorate much faster than normal."

"It does look pretty gruesome," Sherri agreed. "I'm glad we've been ordered to keep our s.p.a.cesuits on. I wouldn't want to be exposed to anything that might be out there."

"I wonder--" Wayne muttered.

"What? What's the matter?"

Wayne pointed to one figure lying on the sand. "See that? What's that over his head?"

"Why--it's a s.p.a.ce helmet!"

"Yeah," said Wayne. "The question is: was he wearing just the helmet, or the whole suit? If he was wearing the whole suit, we're not going to be as well protected as we thought, even with our fancy suits."

Fifteen minutes pa.s.sed slowly before the medics returned, and five minutes more before they had pa.s.sed through the decontamination chambers and were allowed into the ship proper. A ring of tense faces surrounded them as they made their report.

The leader, a tall, bespectacled doctor named Stevelman, was the spokesman. He shrugged when Colonel Petersen put forth the question whose answer everyone waited for.

"I don't know," the medic replied. "I don't know what killed them.

There's dry bones out there, but no sign of anything that might have done it. It's pretty hard to make a quick diagnosis on a skeleton, Colonel."

"What about the one skeleton with the bubble helmet?" Peter Wayne asked.

"Did you see any sign of a full suit on him?"

Stevelman shook his head. "Not a sign, sir."

Colonel Petersen turned and glanced at Lieutenant Jervis. "Do you remember what the circ.u.mstances were, Lieutenant?"

Jervis shrugged. "I don't recall it very clearly, sir. I honestly couldn't tell you whether they were wearing suits or bubble-helmets or anything. I was too upset at the time to make careful observations."

"I understand," Petersen said.

But the medic had a different theory. He pointed at Jervis and said, "That's a point I've meant to make, Lieutenant. You're a trained s.p.a.ce scout. Your psychological records show that you're not the sort of man given to panic or to become confused."

"Are you implying that there's something improper about my statement, Dr. Stevelman?"

The medic held up a hand. "Nothing of the sort, Lieutenant. But since you're not the sort to panic, even in such a crisis as the complete destruction of the entire crew of your scout ship, you must have been ill--partly delirious from fever. Not delirious enough to cause hallucinations, but just enough to impair your judgment."

Jervis nodded. "That is possible," he said.

"Good," said Stevelman. "I have two tentative hypotheses, then." He turned to the colonel. "Should I state them now, Colonel Petersen?"

"There's to be no secrecy aboard this ship, Doctor. I want every man and woman on the ship to know all the facts at all times."

"Very well," the medic said. "I'd suggest the deaths were caused by some unknown virus--or, perhaps, by some virulent poison that occurred occasionally, a poisonous smog of some kind that had settled in the valley for a time and then dissipated."

Wayne frowned and shook his head. Both hypotheses made sense.

"Do you have any suggestions, Doctor?" Petersen said.

"Since we don't have any direct information about why those men died, Colonel, I can't make any definite statements. But I can offer one bit of advice to everyone: _wear your suits and be alert_."

During the week that followed, several groups went out without suffering any ill effects. A short service was held for the eight of the _Mavis_ and then the skeletons were buried in the valley.

They ran a check on the double-nucleus beryllium toward the end of the week, after it had been fairly safely established that no apparent harm was going to come to them. Wayne and Sherri were both in the crew that went outside to set up the detector.

"You man the detector plate," said Major MacDougal, who was in charge of the group, turning to Wayne.

He put his hand on the plate and waited for the guide coordinates to be set. MacDougal fumbled at the base of the detector for a moment, and the machine began picking up eloptic radiations.

Wayne now looked down at the detector plate. "Here we are," he said.

"The dial's oscillating between four and eight, all right. The stuff's here."

MacDougal whistled gently. "It's really sending, isn't it!" He pointed toward the mountaintop. "From up there, too. It's going to be a nice climb. Okay, pack the detector up and let's get back inside."

They entered the airlock and pa.s.sed on into the ship.

"The D-N beryllium up there, sir," Major MacDougal said. "It's going to be a devil of a job to get up to find the stuff."

"That's what Captain Wayne's here for," Petersen said. "Captain, what do you think? Can you get up here?"