[Transcriber Note: This etext was produced from Planet Stories September 1952. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.]

"It's a dead world," Thompson spoke. There was awe in his voice, and in spite of his sure knowledge that nothing could happen to him or to his crew here on this world, there was also somewhere inside of him the trace of a beginning fear.

Standing beside him on the rooftop of the building, Kurkil spoke in a whisper, asking a question that had been better unasked. "What killed it?"

Thompson stirred fretfully. He hadn't wanted to hear this question, he didn't want to hear it now. His gaze went automatically to the trim lines of the space cruiser resting quietly in the square below the building. His spirits lifted at the sight. That was his ship, he was in charge of this far-flung exploring expedition thrown out from Sol Cluster to the fringes of the universe, thrown out by Earth-sired races beginning their long exploration of the mysteries of space and of the worlds of space. There was pride in the sight of the ship and pride in the thought of belonging to this space-ranging race. Then his gaze went over the deserted city radiating in all directions from them and he was aware again of the touch of fear.

Resolutely he turned the feeling out of his mind, began seeking an answer to Kurkil's question.

This place had been a city once. If you counted buildings and streets, tall structures where people might work quietly and effectively, broad avenues leading out to trim homes where they might rest in peace after their labors of the day, if you counted these things as being important, it was still a city. But if you thought that the important element in the make-up of a city was its inhabitants then this place no longer deserved the name.

It had no inhabitants.

"I don't know what killed it," Thompson said. Before landing they had circled this world. From the air they had seen more than a dozen cities such as this one. All of them dead, all of them deserted, all of them with streets overgrown by shrubbery, the pavements buckling from the simple pressure of roots pushing upward, the buildings falling away into ruin for the same reason. But they had seen no inhabitants. They had seen the roads the inhabitants had built to connect their cities, deserted now. They had seen the fields where these people had once worked, fields that now were turning back into forests. They had seen no evidence of landing fields for air craft or space ships. The race that had built the cities had not yet learned the secret of wings.

From the roof of the building where they stood, the only living creatures to be seen were visible through the plastic viewport of the ship below them—Grant, the communication specialist, and Buster, the ship's cat.

Grant had been left to guard the vessel. Buster had been required to remain within the ship, obviously against his will. He had wanted to come with Thompson. A trace of a grin came to Thompson's face at the sight of the cat. He and Buster were firm mutual friends.

"I don't like this place," Kurkil spoke suddenly. "We shouldn't have landed here."

Kurkil paused, then his voice came again, stronger now, and with overtones of fear in it. "There's death here." He slapped at his arm, stared around him.

"What happened?"

"Something bit me." He showed the back of his hand. A tiny puncture was visible.

"Some insect," Thompson said. The matter of an insect bite was of no concern. Kurkil, and every other member of this expedition, were disease-proof. Back in Sol Cluster vaccines and immunizing agents had been developed against every known or conceivable form of germ or virus. Each member of the crew had been carefully immunized. In addition, they had been proofed against stress, against mounting neural pressure resulting from facing real or imaginary danger.

Barring space collision or an accident on a world they were exploring, nothing could happen to them.

"We checked the air, took soil and vegetation samples, before we landed," Thompson said. "There is nothing here that is harmful to a human." There was comfort in the thought.

Kurkil brightened perceptibly. "But, what happened to the race that built this city?"

"I don't know," Thompson answered. A tinge of gruffness crept into his voice as he forced out of his mind the memories of what they had seen in this building they had entered and had climbed. This had once been an office building, a place where the unknown people who had worked here had handled their business transactions and had kept their records. They had seen no bookkeeping machines, none of the elaborate mechanical devices used in Sol Cluster to record the pulse of commerce. This race had not progressed that far. But they had left behind them books written in an unintelligible script, orders for merchandise still neatly pigeonholed, all in good order with no sign of disturbance.

The workers might have left these offices yesterday, except for the carpets of dust that covered everything.

"There isn't even any animal life left," Kurkil spoke.

"I know."

"But what happened? A race that has progressed to the city-building stage doesn't just get wiped out without leaving some indication of what happened to them."

"Apparently they did just that."

"But it's not possible."

"It happened."

"But—"

"There's Neff," Thompson spoke. Far down the avenue below them, three figures had appeared, Neff, Fortune, and Ross. Neff tall and slender, Fortune round like a ball, and Ross built square like a block of concrete. Neff saw them on top of the building and beckoned to them. There was urgency in the gesture.

"They've found something," Thompson said. With Kurkil following him he went hastily out of the building.

"What is it?"

"Come and see," Neff answered. Neff's face was gray. Fortune and Ross were silent.

The building in front of which they were standing had been a house once. The architecture resembled nothing they had ever seen on Earth but the purpose of the structure was obvious. Here somebody had lived. Thompson tried to imagine people living here, the husband coming home in the evening to the dinner prepared by the wife, kids running to meet him. His imagination failed.

"Back here," Neff said.

They went around what had been a house into what had been a garden of some kind, a quiet nook where a family might sprawl in peace. "There," Neff said pointing.

The three skeletons were huddled together in an alcove in front of what had once been a shrine. They lay facing the shrine as if they had died praying. Above them in a niche in a wall was—

"An idol," Kurkil whispered.

"They died praying to their god," Thompson said. He was not aware that he had spoken. Three skeletons....

The bones indicated a creature very similar to the human in structure. A large, a middle-sized, and a small skeleton.

"We think the small one is that of a child," Ross spoke. "We think this was a family."

"I see," Thompson said. "Did you find other skeletons?"

"Many others. We found them almost everywhere but usually tucked away in corners, as if the people had tried to hide from something." His voice went suddenly into uneasy silence.

"Any indication as to the cause of death?"

"None. It apparently came on quite suddenly. We judge that the inhabitants had some warning. At least we do not seem to find enough skeletons for a city of this size, so we estimate that part of the population fled, or tried to."

"I see," Thompson repeated tonelessly. He caught a vague impression that something had passed before his eyes, like a darting flicker of light, and he caught, momentarily, a fast rustle in the air, as of souls passing. His mind was on the flight of this race, the mass hegira they had attempted in an effort to escape from some menace. What menace? "What do you think caused it?"

Ross shrugged, a gesture eloquent with a lack of knowledge and of understanding. "War—"

"No wars were fought on this planet," Neff spoke quickly. "These cities show no evidence of conflict."

"Um," Thompson said. The four men were looking uneasily at him. They were waiting for him to make up his mind, to decide on a course of action.

Thompson did not like his own thinking. Something—the blood-brother of death—had been here on this planet, that much was certain. The evidence was everywhere.

"We will return to the ship," Thompson said.

Grant saw them coming, had the lock open for them. His worried face looked out at them. "What gives here?"

"We don't know," Thompson answered. The cat, Buster, pushed forward between Grant's legs, took a long leap at Thompson's chest, made a twenty-claw safe landing there. "Hi, old fellow, were you worried about me?"

They passed through the lock. "Take her up," Thompson said. "We need a little time to think about this enigma. Maybe we can think better when we're not so close to it."

At his words, relief showed on the faces of the men. "Maybe sometime soon we'll be heading for home?" Kurkil spoke, grinning hopefully.

"You can be certain of that," Thompson said.

The ship lifted, hung miles high in the air above the silent planet. The group considered the problem.

"I vote to make a complete investigation," Grant said. He was full of eager enthusiasm. "There was a race here. Something happened to it. We've got to find out what happened because—" He got no further. Slowly the enthusiasm went from his face. "No, that's not possible," he ended.

"There's no danger of the virus that destroyed this race crossing space to Sol Cluster," Kurkil spoke. "The distance is too great."

"The distance wasn't too great for us to cross it," Fortune spoke.

"Please," Thompson interrupted. "We can't use logic on this situation until we have adequate data. The only data we have—" His voice trailed off into silence as his memory presented him with a facsimile of that data—silent, deserted cities, a world going back to vegetation, three skeletons in front of a shrine.

Abruptly he reached a decision. It was impulsive. "Our tour of exploration is near an end anyhow. We're leaving. We're heading back to Sol Cluster. We'll mark this planet on the star maps for further exploration."

The face of every man present brightened as he made the announcement. Sol Cluster! Home! The green world of Earth across the depths of space. In even the thought there was almost enough magic to wipe out the fear of what they'd seen back there on the deserted planet.

Less than an hour later, the drone of the drivers picked up as the ship, already set on course, began to accelerate in preparation for the jump into hyper-flight. Thompson was in his cabin making a final check of the machine-provided flight data. Buster was in his lap half-asleep. Suddenly the cat jumped from his lap and seemed to pounce on some elusive prey in the room. The cat caught what it was seeking, its jaws crunched, it swallowed.

Thompson stared at the cat from disbelieving eyes. "Buster, are you dreaming? Did you dream there was a mouse in here?"

The cat meowed, came toward him, jumped again into his lap and went back to sleep. Thompson returned to his figures. They were correct.

Over the ship's communication system came the soft throb of a gong. The warning that the jump was coming. In his lap, Buster awakened, instantly sank twenty claws into Thompson's clothing. Thompson reached out and took a firm grip on the hand holds on his desk, began to breathe deeply. The gong sounded again. Final warning that the ship was going into hyper-flight. Thompson took as deep a breath as possible, held it.

The gong went into silence. The ship throbbed. The jump was in progress. Thompson had the dazed impression that every atom in his body tried to turn over at once. For a moment, there was a feeling of intense strain. Then the feeling was gone as the ship and its contents passed into hyper-flight. Thompson began to breathe again. In his lap, Buster relaxed his claw holds, began to purr. Buster was an old hand at taking these jumps.

"EEEEEEyooow!"

The eerie scream that came echoing through the ship seemed to lift up every single strand of hair on Thompson's head. Thompson ran out of the cabin. The scream came again, from the lounge. Thompson entered the lounge just in time to see Kurkil standing in the middle of the room, rip the last remnant of clothing from his body. Revealed under the lights, his skin was turning a vivid green.

Fortune was trying to approach him. Kurkil was warning the man off.

"Stay away, stay away. Don't touch me. You'll get it."

In the split second that was needed for Thompson to take in the situation, the green color flowing over Kurkil's body deepened in intensity.

As the color deepened, the screams bubbling on his lips began to die away. He fell slowly, like a man who is coming unhinged one joint at a time.

He was dead before he hit the floor. Dead so completely that not even a convulsive tremor passed through his body.

A frozen silence held the lounge. For this was a dream, a nightmare, wild, distorted imagery.

Fortune's hand waved vaguely in the direction of Sol Cluster. "It looks as if we're not as bug and stress proof as they said we were."

"What happened?"

"He was sitting there in the chair and I thought he was asleep. Then he was screaming and tearing his clothes off." Ross spread his hands. "I tried to help—"

"I know," Thompson said. He was trying to decide what to do. This ship possessed no facilities for handling the dead. Such a contingency had been thought too remote for consideration. Well, there was the ejection port. "Get sheets," Thompson said. With Fortune and Ross helping, he set about doing what had to be done.

Later, in the lounge, they met to decide what had to be done. Neff, leaving the drivers on automatic control, came up from the engine room. Grant came forward from the control room. If any danger presented itself, warning bells would call them back to their posts.

They were a silent and an uneasy group. Only Buster remained unaffected.

"There seems no doubt that we brought the infection back on board ship with us," Thompson said.

He had stated the obvious. It got the answer it deserved. Silence.

"We also must consider the possibility that another of us, possibly all of us, are infected."

No man stirred, no man spoke. Apparently they hoped they had not heard correctly the words that had been spoken. In Thompson's lap Buster grumbled as if he had understood and did not like what had been said.

"What are we going to do?"

"How can we find out what's causing this disease?"

Two voices came. Then came Fortune's voice. "And even if we find out, what can we do about it? They couldn't do anything about it."

"The fact that the race back there couldn't stop the disease, doesn't mean we can't stop it. We're a different race with a different metabolism and a different body structure—"

"Kurkil had the same metabolism and the same body structure," Ross said.

"We will do what we can," Thompson spoke flatly. In spite of the fact that these men were supposed to be nerve proof, there was panic in the air. He could sense it, knew that it had to be stopped before it got started. Inwardly he cursed the fact that there was no doctor aboard, but he knew only too well the line of reasoning that had led to the omission of a physician.

"We have a medical library," Ross said, tentatively.

"Yes," Fortune spoke. "And it tells you exactly how to treat every conceivable form of accident but it doesn't say a single damned word about infections, and if it did we don't have any medicine to treat them.

Again silence fell. In Thompson's lap, Buster squirmed, dropped to the floor. Tail extended, body low, he moved across the plastic floor as if he were stalking something that lay beyond the open door. "We'll fumigate anyhow," Thompson said. "We'll scour the ship."

There was some relief in action. The clothing that had been worn by the landing party went out through the ejection lock. Inside the ship, the floors, walls, and ceilings were scoured by sweating men who worked feverishly. Fumigants were spread in every room.

With the spreading of the fumigants, spirits began to rise, but even then the signs of stress were still all too obvious. No one knew the incubation period of the virus. Hours only had been needed to bring Kurkil to his death. But days might pass before the virus developed in its next victim.

Months or even years might pass before they were absolutely sure they were free from any chance of infection.

By the time the ship reached Sol Cluster, and the automatic controls stopped its hyper-flight, they might all be dead.

If that happened, the ship's controls would automatically stop its flight. It would be picked up by the far-ranging screens of the space patrol, a ship would be sent out to board it and bring it in.

At the thought of what would happen then, Thompson went hastily forward to the control room. Grant, thin-lipped and nervous, was on duty there. Thompson hastily began plotting a new course. Grant watched over his shoulder.

"Make this change," Thompson said.

"But, Captain—" Grant protested. The man's face had gone utterly white as he realized the implications of this new course. "No. We can't do that. It'll mean—"

"I know what it will mean. And I'm in my right mind, I hope. This course is a precaution, just in case nobody is left alive by the time we reach Sol Cluster."

"But—"

"Make the change," Thompson ordered bluntly.

Reluctantly Grant fed the new course into the computers. A throb went through the vessel as the ship shifted in response.

"We'll come out of hyper-flight in less than three hours," Grant spoke. "Heaven help us if this course is not changed before that time."

"If this course is not changed before that time, Heaven alone can help us. From now on, you're not to leave this control room for an instant."

"Yes, sir."

With Buster following behind him, Thompson left the control room.

"Yoooow!" The scream coming from the lounge this time was in a different key and had a different sound. But the meaning was the same as it had been when Kurkil had screamed. Thompson went forward on the run.

The victim was Ross. Like Kurkil, he was tearing his clothes off. Like Kurkil, he was turning green. When he went down, he did not rise again.

As he stood staring down at Ross, Thompson had the vague impression of whirring wings passing near him. Whispering wings, as if a soul were taking flight.

From the engine room Neff appeared. "I heard somebody scream over the intercom. Oh, I see." His face worked, his jaws moved as if he was trying to speak. But no sound came.

Fortune emerged from his quarters to look down at Ross. "Our fumigating didn't work, huh?"

"Maybe he caught the bug on the planet," Thompson said. He tried to put conviction into his voice. The effort failed. "Get sheets," he said.

There was no prayer. There was no burial ceremony. The body went through the ejection port and disappeared in the vast depths of space.

Thompson returned to his cabin, slumped down at his desk, Fortune and Neff following.

Buster meowed. "Okay, pal." The cat jumped into Thompson's lap.

"I guess there's not much point in trying to kid ourselves any longer," Fortune said. His voice was dull and flat, without tone and without spirit. A muscle in Neff's cheek was twitching.

"I don't understand you," Thompson said.

"Hell, you understand me well enough. The facts are obvious. We've either all got the virus, or it's here in the ship, and we will get it. All we're doing is waiting to see who goes next. What I want to know is—Who'll shove the last man through the ejection port?"

"I don't know," Thompson answered.

"Isn't there anything else we can do?" The tic in Neff's cheek was becoming more pronounced.

"If there is, I don't know—What the hell, Buster?" The cat which had been lying in his lap, suddenly leaped to the floor. Tail extended, crouched, eyes alert, the cat seemed to be trying to follow the flight of something through the air above him.

Very vaguely, very dimly, Thompson caught the rustle of wings.

The actions of the cat, and the sound, sent a wave of utter cold washing over his body.

Before he could move, the cat leaped upward, caught something in snapping jaws.

In the same split second Thompson moved. Before Buster had had time to swallow, Thompson had caught him behind the jaws, forcing them shut. On his desk was a bell jar. He lifted it, thrust the cat's head under it, forced his thumb and forefinger against the jaws of the cat.

The outraged Buster disgorged something. Thompson jerked the cat's head from under the jar, slammed down the rim. The angry cat snarled at him. Neff and Fortune were staring at him from eyes that indicated they thought he had lost his senses. Thompson paid them no attention. He was too busy watching something inside the bell jar even to notice that they existed.

He could not see the creature under the jar.

He knew it could fly but he did not know its shape or size. He could hear it hitting the falls of the jar. And each time it hit the wall, a tiny greenish smudge appeared at the point of impact.

"What—what the hell have you got there?" Neff whispered.

"I don't know for sure. But I think I've got the carrier of the virus."

"What?"

"Watch."

"I can't see anything."

"Nor can I yet, but I can hear it and I can see the places where it hits the wall of the jar. There's something under the jar. Something that Buster has been seeing all along."

"What?"

Thompson pointed at the jar. "One or several of those things came into the ship when the lock was open. We couldn't see them, didn't know they existed. But Buster saw them. He caught one of them in this cabin soon after we took off. I thought he was playing a game to amuse himself, or—" He broke off. From the back of his mind came a fragment of history, now in the forgotten Dark Ages of Earth, whole populations had been ravaged and destroyed by a fever that was carried by some kind of an insect. Did they have some kind of an insect under his jar?

Holding his breath, Thompson watched.

The pounding against the walls of the jar was growing weaker. Then it stopped. On the desk top, a smudge appeared. Wings quavered there, wings that shifted through a range of rainbow colors as they became visible.

As the flutter of the wings stopped the whole creature became visible. Made up of some kind of exceedingly thin tissue that was hardly visible, it was about as big as a humming bird.

Silence held the room. Thompson was aware of his eyes coming to focus on the long pointed bill of the creature.

"Alive it was not visible at all," Fortune whispered. "Dead, you can see it." His voice lifted, picked up overtones of terror. "Say an hour or so ago Ross was complaining that something had bit him."

Like the last remnant of a picture puzzle fitting together, something clicked in Thompson's mind. "And Kurkil. While we were out of the ship something bit him."

Silence again. His eyes went from Neff to Fortune. "Did—"

They shook their heads.

"Then that ties up the package," Thompson whispered. "This creature carried the virus, or poison, or whatever it was. Without being bitten, the virus cannot spread. We've found the cause. We've got it licked."

He was aware of sweat appearing on his face, the sweat of pure relief. He sank back into his chair. Buster, recovering from his indignity at the outrage he had suffered, jumped to the top of the desk, settled down with his nose against the glass, watching the dead creature inside the bell jar.

"He caught one of those things right in this cabin," Thompson whispered. A shudder passed over him and was gone. He had been so close to death, and had not known it. Buster had saved him.

Instead of seeking protection from him, the cat, in a sense, had been protecting him. His gaze centered fondly on the cat.

"What if there are more of those things in the ship?" Fortune spoke.

"We can solve that one," Thompson spoke. "Space suits. And, now that we know what we're looking for, we can clean out the ship. If we don't, Buster will do it for us."

"Space suits!" As if he had heard no more than those two words, Fortune ran from the room. He returned with three suits. They hastily donned them.

"No damned bug can bite through one of these things," Neff said exultantly. "Say, what about Grant? Hadn't we better take him a suit too?"

"I should say so. Fortune...." But Fortune was already leaving the room on his errand. Thompson snapped open the intercom system. "Grant?"

"Yes, what is it?"

"We've found the cause and we've got the disease licked."

Grant's voice a shout coming back from the control room. "Thank God. I've been sitting here watching Sol grow bigger and bigger...." His voice suddenly choked, went into silence, then came again, asking a question. "Is it all right to change course now?"

"Definitely it's all right," Thompson answered. "In fact, it's an order."

An instant later, the ship groaned as the direction of flight was shifted. Thompson took a deep breath, was aware that Neff was staring at him. "What was that he said about watching Sol grow bigger and bigger? Say, what course were we on?"

"Collision course with the sun," Thompson answered.

"What?" Neff gasped. "Do you mean to say that you were going to throw the ship into the sun?"

Slowly Thompson nodded. "I didn't know whether we would be alive or not but I didn't want this ship to enter Sol Cluster and turn loose there the virus that had already depopulated a planet."

He spoke slowly, with the sure knowledge of a desperate danger safely passed. Neff stared at him from round and frightened eyes.

On the desk top Buster gave up his vigil, meowed, and jumped into the captain's lap. With the thick gloves of his space suit clad hands, Thompson fondly stroked him.

Buster arched his back in grateful appreciation and began to purr.