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-b.u.t.ton 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 sc.r.a.ped 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."

CHAPTER 10

THE BOOMERANG CLUE

It was a virus, beyond doubt. The electron microscope told them that, now that they had the substance isolated and could examine it. In the culture tubes in the _Lancet_'s incubators, it would begin to grow nicely, and then falter and die, but when guinea pigs were inoculated in the ship's laboratory, the substance proved its virulence. The animals injected with tiny bits of the substance grew sick within hours and very quickly died.

The call to the Hospital Ship was canceled as the three doctors worked in feverish excitement. Here at last was something they could grapple with, something so common among the races of the galaxy that the doctors felt certain that they could cope with it. Very few, if any, higher life forms existed that did not have some sort of submicroscopic parasite afflicting them. Bacterial infection was a threat on every inhabited world, and the viruses--the tiniest of all submicroscopic organisms--were the most difficult and dangerous of them all.

And yet virus plagues had been stopped before, and they could be stopped again.

Jack radioed down to the planet's surface that the diagnosis had been made; as soon as the proper medications could be prepared, the doctors would land to begin treatment. There was a new flicker of hopefulness in the Bruckian's response, and an appeal to hurry. With renewed energy the doctors went back to the lab to start working on the new data.

But trouble continued to dog them. This was no ordinary virus. It proved resistant to every one of the antibiotics and antiviral agents in the _Lancet_'s stockroom. No drug seemed to affect it, and its molecular structure was different from any virus that had ever been recorded before.

"If one of the drugs would only just slow it up a little, we'd be ahead," Tiger said in perplexity. "We don't have anything that even touches it, not even the purified globulins."

"What about antibodies from the infected people?" Jack suggested. "In every virus disease I've ever heard of, the victim's own body starts making antibodies against the invading virus. If enough antibodies are made fast enough, the virus dies and the patient is immune from then on."

"Well, these people don't seem to be making any antibodies at all,"

Tiger said. "At least not as far as I can see. If they were, at least some of them would be recovering from the disease. So far not a single one has recovered once the thing started. They all just go ahead and die."

"I wonder," Dal said, "if Fuzzy had any defense."

Jack looked up. "How do you mean?"

"Well, Fuzzy was infected, we know that. He might have died too, if we hadn't caught it in time--but as it worked out, he didn't. In fact, he looks pretty healthy right now."

"That's fine for Fuzzy," Jack said impatiently, "but I don't see how we can push the whole population of 31 Brucker VII through a virus filter.

They're flesh-and-blood creatures."

"That's not what I mean," Dal said. "Maybe Fuzzy's body developed antibodies against the virus while he was infected. Remember, he doesn't have a rigid body structure like we do. He's mostly just basic protein, and he can synthesize pretty much anything he wants to or needs to."

Jack blinked. "It's an idea, at least. Is there any way we can get some of his body fluid away from him? Without getting bit, I mean?"

"No problem there," Dal said. "He can regenerate pretty fast if he has enough of the right kind of food. He won't miss an ounce or two of excess tissue."

He took a beaker over to Fuzzy's platform and began squeezing off a little blob of pink material. Fuzzy seemed to sense what Dal wanted; obligingly he thrust out a little pseudopod which Dal pinched off into the beaker. With the addition of a small amount of saline solution, the tissue dissolved into thin, pink suspension.

In the laboratory they found two or three of the guinea pigs in the last stages of the infection, and injected them with a tiny bit of the pink solution. The effect was almost unbelievable. Within twenty minutes all of the injected animals began to perk up, their eyes brighter, nibbling at the food in their cages, while the ones that had not been injected got sicker and sicker.

"Well, there's our answer," Jack said eagerly. "If we can get some of this stuff injected into our friends down below, we may be able to protect the healthy ones from getting the plague, and cure the sick ones as well. If we still have enough time, that is."

They had landing permission from the Bruckian spokesman within minutes, and an hour later the _Lancet_ made an orderly landing on a newly-repaved landing field near one of the central cities on the seventh planet of 31 Brucker.

Tiger and Jack had obviously not exaggerated the strange appearance of the towns and cities on this plague-ridden planet, and Dal was appalled at the ravages of the disease that they had come to fight. Only one out of ten of the Bruckians was still uninfected, and another three out of the ten were clearly in the late stages of the disease, walking about blankly and blindly, stumbling into things in their paths, falling to the ground and lying mute and helpless until death came to release them.

Under the glaring red sun, weary parties of stretcher bearers went about the silent streets, moving their grim cargo out to the ma.s.s graves at the edge of the city.

The original spokesman who had come up to the _Lancet_ was dead, but another had taken his place as negotiator with the doctors--an older, thinner Bruckian who looked as if he carried the total burden of his people on his shoulders. He greeted them eagerly at the landing field.

"You have found a solution!" he cried. "You have found a way to turn the tide--but hurry! Every moment now is precious."

During the landing procedures, Dal had worked to prepare enough of the precious antibody suspension, with Fuzzy's co-operation, to handle a large number of inoculations. By the time the ship touched down he had a dozen flasks and several hundred syringes ready. Hundreds of the unafflicted people were crowding around the ship, staring in open wonder as Dal, Jack and Tiger came down the ladder and went into close conference with the spokesman.

It took some time to explain to the spokesman why they could not begin then and there with the ma.s.s inoculations against the plague. First, they needed test cases, in order to make certain that what they thought would work in theory actually produced the desired results. Controls were needed, to be certain that the antibody suspension alone was bringing about the changes seen and not something else. At last, orders went out from the spokesman. Two hundred uninfected Bruckians were admitted to a large roped-off area near the ship, and another two hundred in late stages of the disease were led stumbling into another closed area. Preliminary skin-tests of the antibody suspension showed no sign of untoward reaction. Dal began filling syringes while Tiger and Jack started inoculating the two groups.

"If it works with these cases, it will be simple to immunize the whole population," Tiger said. "From the amounts we used on the guinea pigs, it looks as if only tiny amounts are needed. We may even be able to train the Bruckians to give the injections themselves."

"And if it works we ought to have a brand new medical service contract ready for signature with Hospital Earth," Jack added eagerly. "It won't be long before we have those Stars, you wait and see! If we can only get this done fast enough."

They worked feverishly, particularly with the group of terminal cases.

Many were dying even as the shots were being given, while the first symptoms of the disease were appearing in some of the unafflicted ones.

Swiftly Tiger and Jack went from patient to patient while Dal kept check of the names, numbers and locations of those that were inoculated.

And even before they were finished with the inoculations, it was apparent that they were taking effect. Not one of the infected patients died after inoculation was completed. The series took three hours, and by the time the four hundred doses were administered, one thing seemed certain: that the antibody was checking the deadly march of the disease in some way.

The Bruckian spokesman was so excited he could hardly contain himself; he wanted to start bringing in the rest of the population at once.

"We've almost exhausted this first batch of the material," Dal told him.

"We will have to prepare more--but we will waste time trying to move a whole planet's population here. Get a dozen aircraft ready, and a dozen healthy, intelligent workers to help us. We can show them how to use the material, and let them go out to the other population centers all at once."

Back aboard the ship they started preparing a larger quant.i.ty of the antibody suspension. Fuzzy had regenerated back to normal weight again, and much to Dal's delight had been splitting off small segments of pink protoplasm in a circle all around him, as though antic.i.p.ating further demands on his resources. A quick test-run showed that the antibody was also being regenerated. Fuzzy was voraciously hungry, but the material in the second batch was still as powerful as in the first.

The doctors were almost ready to go back down, loaded with enough inoculum and syringes to equip themselves and a dozen field workers when Jack suddenly stopped what he was doing and c.o.c.ked an ear toward the entrance lock.

"What's wrong?" Dal said.

"Listen a minute."

They stopped to listen. "I don't hear anything," Tiger said.

Jack nodded. "I know. That's what I mean. They were hollering their heads off when we came back aboard. Why so quiet now?"

He crossed over to the viewscreen scanning the field below, and flipped on the switch. For a moment he just stared. Then he said: "Come here a minute. I don't like the looks of this at all."