Slowly and patiently they drew the story from the emissary from the seventh planet of 31 Brucker.

The small, monkey-like creature was painfully shy; he required constant reassurance that the doctors did not mind being called, that they wanted to help, and that a contract was not necessary in an emergency. Even at that the spokesman was reluctant to give details about the plague and about his stricken people. Every bit of information had to be extracted with patient questioning.

By tacit consent the doctors did not even mention the strange fact that this very planet had been explored by a Confederation ship eight hundred years before and no sign of intelligent life had been found. The little creature before them seemed ready to turn and bolt at the first hint of attack or accusation. But bit by bit, a picture of the current situation on the planet developed.

Whoever they were and wherever they had been when the Confederation ship had landed, there was unquestionably an intelligent race now inhabiting this lonely planet in the outer reaches of the solar system of 31 Brucker. There was no doubt of their advancement; a few well-selected questions revealed that they had control of atomic power, a working understanding of the nature and properties of contra-terrene matter, and a workable star drive operating on the same basic principle as Earth's Koenig drive but which the Bruckians had never really used because of their shyness and fear of contact with other races. They also had an excellent understanding, thanks to their eavesdropping on Confederation interstellar radio chatter, of the existence and functions of the Galactic Confederation of worlds, and of Hospital Earth's work as physician to the galaxy.

But about Bruckian anatomy, physiology or biochemistry, the little emissary would tell them nothing. He seemed genuinely frightened when they pressed him about the physical make-up of his people, as though their questions were somehow scraping a raw nerve. He insisted that his people knew nothing about the nature of the plague that had stricken them, and the doctors could not budge him an inch from his stand.

But a plague had certainly struck.

It had begun six months before, striking great masses of the people. It had walked the streets of the cities and the hills and valleys of the countryside. First three out of ten had been stricken, then four, then five. The course of the disease, once started, was invariably the same: first illness, weakness, loss of energy and interest, then gradually a fading away of intelligent responses, leaving thousands of creatures walking blank-faced and idiot-like about the streets and countryside. Ultimately even the ability to take food was lost, and after an interval of a week or so, death invariably ensued.

Finally the doctors retired to the control room for a puzzled conference. "It's got to be an organism of some sort that's doing it," Dal said. "There couldn't be an illness like this that wasn't caused by some kind of a parasitic germ or virus."

"But how do we know?" Jack said. "We know nothing about these people except what we can see. We're going to have to do a complete biochemical and medical survey before we can hope to do anything."

"But we aren't equipped for a real survey," Tiger protested.

"We've got to do it anyway," Jack said. "If we can just learn enough to be sure it's an infectious illness, we might stand a chance of finding a drug that will cure it. Or at least a way to immunize the ones that aren't infected yet. If this is a virus infection, we might only need to find an antibody for inoculation to stop it in its tracks. But first we need a good look at the planet and some more of the people—both infected and healthy ones. We'd better make arrangements as fast as we can."

An hour later they had reached an agreement with the Bruckian emissary. The Lancet would be permitted to land on the planet's surface as soon as the doctors were satisfied that it was safe. For the time being the initial landings would be made in the patrol ship's lifeboats, with the Lancet in orbit a thousand miles above the surface. Unquestionably the first job was diagnosis, discovering the exact nature of the illness and studying the afflicted people. This responsibility rested squarely on Jack's shoulders; he was the diagnostician, and Dal and Tiger willingly yielded to him in organizing the program.

It was decided that Jack and Tiger would visit the planet's surface at once, while Dal stayed on the ship and set up the reagents and examining techniques that would be needed to measure the basic physical and biochemical characteristics of the Bruckians.

Yet in all the excitement of planning, Dal could not throw off the lingering shadow of doubt in his mind, some instinctive voice of caution that seemed to say watch out, be careful, go slowly! This may not be what it seems to be; you may be walking into a trap....

But it was only a faint voice, and easy to thrust aside as the planning went ahead full speed.

It did not take very long for the crew of the Lancet to realize that there was something very odd indeed about the small, self-effacing inhabitants of 31 Brucker VII.

In fact, "odd" was not really quite the proper word for these creatures at all. No one knew better than the doctors of Hospital Earth that oddness was the rule among the various members of the galactic civilization. All sorts and varieties of life-forms had been discovered, described and studied, each with its singular differences, each with certain similarities, and each quite "odd" in reference to any of the others.

In Dal this awareness of the oddness and difference of other races was particularly acute. He knew that to Tiger and Jack he himself seemed odd, both anatomically and in other ways. His fine gray fur and his four-fingered hands set him apart from them—he would never be mistaken for an Earthman, even in the densest fog. But these were comprehensible differences. His close attachment to Fuzzy was something else, and still seemed beyond their ability to understand.

He had spent one whole evening patiently trying to make Jack understand just how his attachment to the little pink creature was more than just the fondness of a man for his dog.

"Well, what would you call it, then?"

"Symbiosis is probably the best word for it," Dal had replied. "Two life-forms live together, and each one helps the other—that's all symbiosis is. Together each one is better off than either one would be alone. We all of us live in symbiosis with the bacteria in our digestive tracts, don't we? We provide them with a place to live and grow, and they help us digest our food. It's a kind of a partnership—and Fuzzy and I are partners in the same sort of way."

Jack had argued, and then lost his temper, and finally grudgingly agreed that he supposed he would have to tolerate it even if it didn't make sense to him.

But the creatures on 31 Brucker VII were "odd" far beyond the reasonable limits of oddness—so far beyond it that the doctors could not believe the things that their eyes and their instruments were telling them.

When Tiger and Jack came back to the Lancet after their first trip to the planet's surface, they were visibly shaken. Geographically, they had found it just as it had been described in the exploratory reports—a barren, desert land with only a few large islands of vegetation in the equatorial regions.

"But the people!" Jack said. "They don't fit into any kind of pattern. They've got houses—at least I guess you'd call them houses—but every one of them is like every other one, and they're all crammed together in tight little bunches, with nothing for miles in between. They've got an advanced technology, a good communications system, manufacturing techniques and everything, but they just don't use them."

"It's more than that," Tiger said. "They don't seem to want to use them."

"Well, it doesn't add up, to me," Jack said. "There are thousands of towns and cities down there, all of them miles apart, and yet they had to go dig an old rusty jet scooter out of storage and get the motor rebuilt just specially to take us from one place to another. I know things can get disorganized with a plague in the land, but this plague just hasn't been going on that long."

"What about the sickness?" Dal asked. "Is it as bad as it sounded?"

"Worse, if anything," Tiger said gloomily. "They're dying by the thousands, and I hope we got those suits of ours decontaminated, because I don't want any part of this disease."

Graphically, he described the conditions they had found among the stricken people. There was no question that a plague was stalking the land. In the rutted mud roads of the villages and towns the dead were piled in gutters, and in all of the cities a deathly stillness hung over the streets. Those who had not yet succumbed to the illness were nursing and feeding the sick ones, but these unaffected ones were growing scarcer and scarcer. The whole living population seemed resigned to hopelessness, hardly noticing the strangers from the patrol ship.

But worst of all were those in the final stages of the disease, wandering vaguely about the street, their faces blank and their jaws slack as though they were living in a silent world of their own, cut off from contact with the rest. "One of them almost ran into me," Jack said. "I was right in front of him, and he didn't see me or hear me."

"But don't they have any knowledge of antisepsis or isolation?" Dal asked.

Tiger shook his head. "Not that we could see. They don't know what's causing this sickness. They think that it's some kind of curse, and they never dreamed that it might be kept from spreading."

Already Tiger and Jack had taken the first routine steps to deal with the sickness. They gave orders to move the unaffected people in every town and village into isolated barracks and stockades. For half a day Tiger tried to explain ways to prevent the spread of a bacteria or virus-borne disease. The people had stared at him as if he were talking gibberish; finally he gave up trying to explain, and just laid down rules which the people were instructed to follow. Together they had collected standard testing specimens of body fluids and tissue from both healthy and afflicted Bruckians, and come back to the Lancet for a breather.

Now all three doctors began work on the specimens. Cultures were inoculated with specimens from respiratory tract, blood and tissue taken from both sick and well. Half a dozen fatal cases were brought to the ship under specially controlled conditions for autopsy examination, to reveal both the normal anatomical characteristics of this strange race of people and the damage the disease was doing. Down on the surface Tiger had already inoculated a dozen of the healthy ones with various radioactive isotopes to help outline the normal metabolism and biochemistry of the people. After a short sleep period on the Lancet, he went back down alone to follow up on these, leaving Dal and Jack to carry on the survey work in the ship's lab.

It was a gargantuan task that faced them. They knew that in any race of creatures they could not hope to recognize the abnormal unless they knew what the normal was. That was the sole reason for the extensive biomedical surveys that were done on new contract planets. Under normal conditions, a survey crew with specialists in physiology, biochemistry, anatomy, radiology, pharmacology and pathology might spend months or even years on a new planet gathering base-line information. But here there was neither time nor facilities for such a study. Even in the twenty-four hours since the patrol ship arrived, the number of dead had increased alarmingly.

Alone on the ship, Dal and Jack found themselves working as a well organized team. There was no time here for argument or duplicated efforts; everything the two doctors did was closely co-ordinated. Jack seemed to have forgotten his previous antagonism completely. There was a crisis here, and more work than three men could possibly do in the time available. "You handle anatomy and pathology," Jack told Dal at the beginning. "You can get the picture five times as fast as I can, and your pathology slides are better than most commercial ones. I can do the best job on the cultures, once I get the growth media all set up."

Bit by bit they divided the labor, checking in with Tiger by radio on the results of the isotopes studies he was running on the planet's surface. Bit by bit the data was collected, and Earthman and Garvian worked more closely than ever before as the task that faced them appeared more and more formidable.

But the results of their tests made no sense whatever. Tiger returned to the ship after forty-eight hours with circles under his eyes, looking as though he had been trampled in a crowd. "No sleep, that's all," he said breathlessly as he crawled out of his decontaminated pressure suit. "No time for it. I swear I ran those tests a dozen times and I still didn't get any answers that made sense."

"The results you were sending up sounded plenty strange," Jack said. "What was the trouble?"

"I don't know," Tiger said, "but if we're looking for a biological pattern here, we haven't found it yet as far as I can see."

"No, we certainly haven't," Dal exploded. "I thought I was doing something wrong somehow, because these blood chemistries I've been doing have been ridiculous. I can't even find a normal level for blood sugar, and as for the enzyme systems...." He tossed a sheaf of notes down on the counter in disgust. "I don't see how these people could even be alive, with a botched-up metabolism like this! I've never heard of anything like it."

"What kind of pathology did you find?" Tiger wanted to know.

"Nothing," Dal said. "Nothing at all. I did autopsies on the six that you brought up here and made slides of every different kind of tissue I could find. The anatomy is perfectly clear cut, no objections there. These people are very similar to Earth-type monkeys in structure, with heart and lungs and vocal cords and all. But I can't find any reason why they should be dying. Any luck with the cultures?"

Jack shook his head glumly. "No growth on any of the plates. At first I thought I had something going, but if I did, it died, and I can't find any sign of it in the filtrates."

"But we've got to have something to work on," Tiger said desperately. "Look, there are some things that always measure out the same in any intelligent creature no matter where he comes from. That's the whole basis of galactic medicine. Creatures may develop and adapt in different ways, but the basic biochemical reactions are the same."

"Not here, they aren't," Dal said. "Take a look at these tests!"

They carried the heap of notes they had collected out into the control room and began sifting and organizing the data, just as a survey team would do, trying to match it with the pattern of a thousand other living creatures that had previously been studied. Hours passed, and they were farther from an answer than when they began.

Because this data did not fit a pattern. It was different. No two individuals showed the same reactions. In every test the results were either flatly impossible or completely the opposite of what was expected.

Carefully they retraced their steps, trying to pinpoint what could be going wrong.

"There's got to be a laboratory error," Dal said wearily. "We must have slipped up somewhere."

"But I don't see where," Jack said. "Let's see those culture tubes again. And put on a pot of coffee. I can't even think straight any more."

Of the three of them, Jack was beginning to show the strain the most. This was his special field, the place where he was supposed to excel, and nothing was happening. Reports coming up from the planet were discouraging; the isolation techniques they had tried to institute did not seem to be working, and the spread of the plague was accelerating. The communiquÉs from the Bruckians were taking on a note of desperation.

Jack watched each report with growing apprehension. He moved restlessly from lab to control room, checking and rechecking things, trying to find some sign of order in the chaos.

"Try to get some sleep," Dal urged him. "A couple of hours will freshen you up a hundred per cent."

"I can't, I've already tried it," Jack said.

"Go ahead. Tiger and I can keep working on these things for a while."

"No, no, it's not that," Jack said. "Without a diagnosis, we can't do a thing. Until we have that, our hands are tied, and we aren't even getting close to it. We don't even know whether this is a bacteria, or a virus, or what. Maybe the Bruckians are right. Maybe it's a curse."

"I don't think the Black Service of Pathology would buy that for a diagnosis," Tiger said sourly.

"The Black Service would choke on it—but what other answer do we have? You two have been doing all you can, but diagnosis is my job. I'm supposed to be good at it, but the more we dig into this, the farther away we seem to get."

"Do you want to call for help?" Tiger said.

Jack shook his head helplessly. "I'm beginning to think we should have called for help a long time ago," he said. "We're into this over our heads now and we're still going down. At the rate those people are dying down there, we don't have time to call for help now." He stared at the piles of notes on the desk and his face was very white. "I don't know, I just don't know," he said. "The diagnosis on this thing should have been duck soup. I thought it was going to be a real feather in my cap, just walking in and nailing it down in a few hours. Well, I'm whipped. I don't know what to do. If either of you can think of an answer, it's all yours, and I'll admit it to Black Doctor Tanner himself."

It was bitter medicine for Blue Doctor Jack Alvarez to swallow, but that fact gave no pleasure to Dal or Tiger now. They were as baffled as Jack was, and would have welcomed help from anyone who could offer it.

And, ironically, the first glimpse of the truth came from the direction they least expected.

From the very beginning Fuzzy had been watching the proceedings from his perch on the swinging platform in the control room. If he sensed that Dal Timgar was ignoring him and leaving him to his own devices much of the time, he showed no sign of resentment. The tiny creature seemed to realize that something important was consuming his master's energy and attention, and contented himself with an affectionate pat now and then as Dal went through the control room. Everyone assumed without much thought that Fuzzy was merely being tolerant of the situation. It was not until they had finally given up in desperation and Tiger was trying to contact a Hospital Ship for help, that Dal stared up at his little pink friend with a puzzled frown.

Tiger put the transmitter down for a moment. "What's wrong?" he said to Dal. "You look as though you just bit into a rotten apple."

"I just remembered that I haven't fed him for twenty-four hours," Dal said.

"Who? Fuzzy?" Tiger shrugged. "He could see you were busy."

Dal shook his head. "That wouldn't make any difference to Fuzzy. When he gets hungry, he gets hungry, and he's pretty self-centered. It wouldn't matter what I was doing, he should have been screaming for food hours ago."

Dal walked over to the platform and peered down at his pink friend in alarm. He took him up and rested him on his shoulder, a move that invariably sent Fuzzy into raptures of delight. Now the little creature just sat there, trembling and rubbing half-heartedly against Dal's neck.

Dal held him out at arm's length. "Fuzzy, what's the matter with you?"

"Do you think something's wrong with him?" Jack said, looking up suddenly. "Looks like he's having trouble keeping his eyes open."

"His color isn't right, either," Tiger said. "He looks kind of blue."

Quite suddenly the little black eyes closed and Fuzzy began to tremble violently. He drew himself up into a tight pink globule as the fuzz-like hair disappeared from view.

Something was unmistakably wrong. As he held the shivering creature, Dal was suddenly aware that something had been nibbling at the back of his mind for hours. Not a clear-cut thought, merely an impression of pain and anguish and sickness, and now as he looked at Fuzzy the impression grew so strong it almost made him cry out.

Abruptly, Dal knew what he had to do. Where the thought came from he didn't know, but it was crystal clear in his mind. "Jack, where is our biggest virus filter?" he asked quietly.

Jack stared at him. "Virus filter? I just took it out of the autoclave an hour ago."

"Get it," Dal said, "and the suction machine too. Quickly!"

Jack went down the corridor like a shot, and reappeared a moment later with the big porcelain virus filter and the suction tubing attached to it. Swiftly Dal dumped the limp little creature in his hand into the top of the filter jar, poured in some sterile saline, and started the suction.

Tiger and Jack watched him in amazement. "What are you doing?" Tiger said.

"Filtering him," Dal said. "He's infected. He must have been exposed to the plague somehow, maybe when our little Bruckian visitor came on board the other day. And if it's a virus that's causing this plague, the virus filter ought to hold it back and still let Fuzzy's molecular structure through."

They watched and sure enough a bluish-pink fluid began moving down through the porcelain filter, and dripping through the funnel into the beaker below. Each drop coalesced in the beaker as it fell until Fuzzy's whole body had been sucked through the filter and into the jar below. He was still not quite his normal pink color, but as the filter went dry, a pair of frightened shoe-button eyes appeared and he poked up a pair of ears. Presently the fuzz began appearing on his body again.

And on the top of the filter lay a faint gray film. "Don't touch it!" Dal said. "That's real poison." He slipped on a mask and gloves, and scraped a bit of the film from the filter with a spatula. "I think we have it," he said. "The virus that's causing the plague on this planet."