Denny Olear was playing blackjack when the colonel’s orderly found him. He hastily buttoned his tunic and in a few minutes, alert and very military, was standing at attention in the little office on the ground floor of the Denver I. F. P. barracks. His swanky blue uniform fitted without a wrinkle. His little round skullcap was perched at the regulation angle.

“Olear,” said the colonel, “they’re having a little trouble at the Blue River Station, Mercury.”

“Trouble? Uh-huh,” Olear said placidly.

The colonel looked him over. He saw a man past his first youth. Thirty-five, possibly forty. Olear was well-knit, sandy-haired, not over five feet six inches in height. His hair was close-cropped, his features phlegmatic, his eyes a light blue with thick, short, light-colored lashes, his teeth excellent. A scar, dead white on a brown cheekbone, was a reminder of an “encounter” with one of the numerous sauriens of Venus.

“I’m sending you,” explained the colonel, “because you’re more experienced, and not like some of these kids, always spoiling for a fight. There’s something queer about this affair. Morones, factor of the Blue River post, reports that his assistant has disappeared. Vanished. Simply gone. But only three months ago the former factor--Morones was his assistant--disappeared. No hide nor hair of him. Morones reported to the company, the Mercurian Trading Concession, and they called me. Something, they think, is rotten.”

“Yes, sir.”

“I guess I needn’t tell you,” the colonel went on, “that you have to use tact. People don’t seem to appreciate the Force. What with the lousy politicians begrudging every cent we get, and a bunch of suspicious foreign powers afraid we’ll get too good--”

“Yeah, I know. Tact, that’s my motto. No rough stuff.” He saluted, turned on his heel.

“Just a minute!” The colonel had arisen. He was a fine, ascetic type of man. He held out his hand.

“Good-by, Olear. Watch yourself!”

When Olear had taken his matter-of-fact departure the colonel ran his fingers through his whitening hair. In the past several months he had sent five of his best men on dangerous missions--missions requiring tact, courage, and, so it seemed, very much luck. And only two of the five had come back. In those days the Interplanetary Flying Police did not enjoy the tremendous prestige it does now. The mere presence of a member of the Force is enough, in these humdrum days of interplanetary law and order, to quell the most serious disturbance anywhere in the solar system. But it was not always thus. This astounding prestige had to be earned with blood and courage, in many a desperate and lonely battle; had to be snatched from the dripping jaws of death.

Olear checked over his flying ovoid, got his bearings from the port astronomer, set his coordinate navigator and shoved off. Two weeks later he plunged into the thick, misty atmosphere on the dark side of Mercury.

Ancient astronomers had long suspected that Mercury always presented the same side to the sun, though they were ignorant that the little planet had water and air. Its sunward side is a dreary, sterile, hot and hostile desert. Its dark side is warm and humid, and resembles to some extent the better known jungles and swamps of Venus. But it has a favored belt, some hundreds of miles wide, around its equator, where the enormous sun stays perpetually in one spot on the horizon. Sunward is the blinding glare of the desert; on the dark side, enormous banks of lowering clouds. On the dark margin of this belt are the “ringstorms,” violent thunderstorms that never cease. They are the source of the mighty rivers which irrigate the tropical habitable belt and plunge out, boiling, far into the desert.

Olear’s little ship passed through the ringstorms, and he did not take over the controls until he recognized the familiar mark of the trading company, a blue comet on the aluminum roof of one of the larger buildings. Visibility was good that day, but despite the unusual clarity of the atmosphere there was a suggestion of the sinister about the lifeless scene--the vast, irresistible river, the riotously colored jungle roof. The vastness of nature dwarfed man’s puny work. One horizon flashed incessantly with livid lightning, the other was one blinding blaze of the nearby sun. And almost lost below in the savage landscape was man’s symbol of possession, a few metal sheds in a clear, fenced space of a few acres.

Olear cautiously checked speed, skimmed over the turbid surface of the great river, and set her down on the ground within the compound. With his pencil-like ray-tube in his hand he stepped out of the hatchway.

A Mercurian native came out of the residence, presently, his hands together in the peace sign. For the benefit of Earthlubbers whose only knowledge of Mercury is derived from the teleview screen, it should be explained that Mercurians are not human, even if they do slightly resemble us. They hatch from eggs, pass one life-phase as frog-like creatures in their rivers, and in the adult stage turn more human in appearance. But their skin remains green and fish-belly white. There is no hair on their warty heads. Their eyes have no lids, and have a peculiar dead, staring look when they sleep. And they carry a peculiar, fishy odor with them at all times.

This Mercurian looked at Olear seemingly without interest.

“Where is Morones?” the officer inquired.

“Morones?” the native piped, in English. “Inside. He busy.”

“All right. I’m coming in.”

“He busy.”

“Yeah, move over.”

Though the native was a good six inches taller than Olear he stepped aside when the officer pushed him. Men--and Mercurians--had a way of doing that when they looked into those colorless eyes. They were not as phlegmatic as the face. Morones was sitting in his office.

“Well, I’m here,” Olear announced, helping himself to a chair.

“Yes”--sourly. “Who invited you?”

Olear looked at the factor levelly, appraising him. A big man, fat, but the fat well distributed. Saturnine face, dark hair, dark and bristly beard. The kind that thrived where other men became weak and fever-ridden. Also, to judge by his present appearance, an unpleasant companion and a nasty enemy.

“Don’t see what difference it makes to you,” Olear answered in his own good time; “but the company invited me.”

“They would!” Morones growled. His eyes flickered to the door, and quick as a cat, Olear leaped to one side, his ray-pencil in his hand.

Morones had not moved, and in the door stood the native, motionless and without expression. Morones laughed nastily.

“Kind of jumpy, eh? What is it, Nargyll?”

Nargyll burst into a burbling succession of native phrases, which Olear had some difficulty following.

“Nargyll wants to move your ship into one of the sheds, but the activator key’s gone.”

“Yeah, I know,” Olear assented casually. “I got it. Leave the ship till I get ready. Then I’ll put it away. Get out, Nargyll.”

The native, hesitated, then on the lift of Morones’ eyebrows departed. Olear shifted a chair so that he could watch both Morones and the door. He reopened the conversation easily:

“Well, we understand each other. You don’t want me here and I’m here. So what are you going to do about it?”

Morones flushed. He struggled to keep his temper down.

“What do you want to know?”

“What happened to the factor who was here before you?”

“I don’t know. The translucene wasn’t coming in like it should. Sammis went out into the jungle for a palaver with the chiefs to find out why. And he didn’t come back.”

“You didn’t find out where he went?”

“I just told you,” Morones said impatiently, “he went out to see the native chiefs.”

“Alone?”

“Of course, alone. There were only two of us Earthmen here. Couldn’t abandon this post to the wogglies, could we? Not that it’d make much difference. Except for Nargyll, none’ll come near.”

“You never heard of him again?”

“No! Dammit, no! Say, didn’t they have any dumber strappers around than you? I told you once--I tell you again--I never saw hide nor hair of him after that.”

“Aw-right, aw-right!” Olear regarded Morones placidly. “And so you took the job of factor and radioed for an assistant, and when the assistant came he disappeared.”

Morones grunted, “He went out to get acquainted with the country and didn’t come back.”

Olear masked his close scrutiny of the factor under his idle and expressionless gaze. He was not ready to jump to the conclusion that Morones’ uneasiness sprang from a sense of guilt. Guilty or not, he had a right to feel uneasy. The man would be dense indeed if he did not realize he was in line for suspicion, and he did not look dense. Indeed, he was obviously a shrewd character.

“Let me see your ‘lucene.”

Morones rose. Despite his bulk he stepped nimbly. He had the nimbleness of a Saturnian bear, which is great, as some of the earlier explorers learned to their dismay.

“That’s the first sensible question you’ve asked,” Morones snorted. “Take a look at our ‘lucene. Ha! Have a good look!”

He led the way across the compound, waved his hand before the door of a strongly built shed in a swift, definite combination, and the door opened, revealing the interior. He waved invitingly.

“You go first,” Olear said.

With a sneer Morones stepped in. “You’re safe, boy, you’re safe.”

Olear looked at the small pile on the floor in astonishment. Instead of the beautiful, semi-transparent chips of translucene, the dried sap of a Mercurian tree which is invaluable to the world as the source of an unfailing cancer cure, there were only a few dirty, dried up shavings, hardly worth shipping back to Earth for refining. The full significance of the affair began to dawn on the officer. The translucene trees grew only in this favored section of Mercury, and the Earth company had a monopoly of the entire supply. Justly, for only on Earth was cancer known, and it was on the increase. That small, almost useless pile on the floor connoted a terrible drug famine for the human race.

Morones’ smile might have been a grin of satisfaction, at Olear’s question:

“Is that all you’ve bought since the last freighter was here?”’

“It is,” he replied. “The last load went off six months ago, and this here shed should be full to the eaves. There’ll be hell to pay.”

“It may not be tactful,” Olear remarked, “but if you’ve got your takings cached away somewhere to hold up the Earth for a big ransom, you’d better come across right now. You can’t get by with it, fellow. You should have close to six million dollars’ worth of it, and you can’t get away. You just can’t.”

Morones controlled his anger with an effort.

“Like any dumb strapper, you’ve got your mind made up, ain’t you? Well, go ahead. Get something on me. Here I was almost set to give you a lead that might get you somewhere. And you come shooting off--trying to make out I stole the ‘lucene and killed those two fellows, eh? Go ahead! Get something on me! But not on Company grounds. You’re leaving now!”

With that he made a lunge at the officer, quite beside himself with rage. Olear could have burnt him down, but he was far too experienced for such an amateurish trick. Instead he ducked to evade Morones’ blow. But the big man was as agile as a panther. In mid-air, so it seemed, he changed his direction of attack. The big fist swept downward, striking Olear’s head a glancing blow.

But the men of the Force have always been fighters, whatever their shortcomings as diplomats. Olear countered with a strong right to the body, thudding solidly, for Morones’ softness did not go far below the surface. The factor whirled instantly, but not quite fast enough to bar the door. Olear was out and inside his ship in a few seconds, slamming the hatch.

“Tact!” he grinned to himself, inserting the activator key. “Tact is what a fella needs.” The little space flier shot aloft, until the tiny figure of the factor stopped shaking its fist and entered the residence. The post had a flier of its own, of course, but Morones was too wise to use it in pursuit.

Olear considered what was best to do. Of course he could have placed Morones under arrest; could still do it; but that would not solve the mystery of the two deaths and the missing ‘lucene. If the choleric factor was really guilty of the crimes, it would be better to let him go his way in the hope that he would betray himself. Olear regretted that he had not kept his tongue under closer curb. But there was no use regretting. Perhaps, after all, he ought to turn back to pump Morones for some helpful information.

His mind made up, he descended again until he was hovering a few feet from the ground.

“Morones!” he called. “Morones!” He held the hatch open.

Morones came to the door of the residence. He had a tube in his hand, a long-range weapon.

“Morones,” Olear declared pompously. “I place you under arrest!”

The effect was instantaneous. Morones lifted the tube, and a glimmering, iridescent beam sprang out. The ship was up and away in a second, lurching and shivering uncomfortably every time the beam struck it in its upward flight. A good few seconds continued impingement...

But a miss is as good as a light-year. Miles high, Olear looked into his telens. Morones had laid aside his tube and was working with an instrument like a twin transit. Plotting the ship’s course, naturally. Olear set his course for the Earth, and kept on it for a good twenty-four hours. Morones, if he was still watching him, would think he’d gone back for reinforcements. Such an assumption would be incredible now, but that was before the I. F. P. had achieved its present tremendous reputation.

Beyond observation range, Olear curved back toward Mercury again, and was almost inside its atmosphere when he made a discovery that caused him to lose for a moment his natural indifference, and to clamp his jaws in anger. The current oxygen tank became empty, and when he removed it from the rack and put in a new one he found someone had let out all of this essential gas. The valve of every one of the spare tanks had been opened. Had Olear actually continued on his way to Earth he would have perished miserably of suffocation long before he could have returned to the Mercurian atmosphere. The officer whistled tunelessly through his teeth as he considered this fact.

The visibility was by this time normal; that is, so poor it would have been possible to land very close to the trading station. Olear was taking no chances, however, and came down a good three Earth miles away. The egg-shaped hull sank through the glossy, brilliant treetops, through twisted vines, and was buried in the dank gloom of the jungle. Here it might remain hidden for a hundred years.

The twilight of the jungle was almost darkness. Landmarks were not. But Olear made a few small, inconspicuous marks on trees with his knife until he came to an outcropping rock. He had noticed the scarlike white of it slashing through the jungle from the air, and used it as a guide to direct his stealthy return to the trading post. His belt chronometer told him it would be about time for Morones to get up from his “night’s” sleep. A little discreet observation might tell much.

Long before he reached the compound, Olear heard the rushing of the great Blue River in its headlong plunge to the corrosive heat of the desert. And then, through the mists, he glimpsed the white metal walls of the Company sheds.

He climbed a tree and for a long time watched patiently, lying prone on a limb. Blood-sucking insects tortured him, and flat tree-lice, resembling discs with legs, crawled over him inquisitively. Olear tolerated them with stoic indifference until at last his patience was rewarded. Morones was coming out of the compound. He was alone and obviously did not suspect that he was being watched, for he stepped out briskly. Once in the jungle he walked even faster, watching out warily for the panther-like carnivora that were the most dangerous to man on Mercury.

Olear shinned to the ground and followed cautiously. Morones had his ray-tube with him, as any traveler in these jungles did. Olear could and did draw fast, but a dead trader would be valueless to him in his investigation, so he stalked him with every faculty strained to maintain complete silence. Often, in occasional clearings where the brown darkness grew less, he had to grovel on the slimy ground, picking up large bacteria that could be seen with the naked eye, and which left tiny, festering red marks on the skin. Mercury has no snakes.

The trader seemed to be heading for higher ground, for the path led ever upward, though not far from the tossing waters of the river. And then, suddenly, he disappeared.

Olear did not immediately hurry after him. A canny fugitive, catching sight of his pursuer, might suddenly drop to the ground and squirm to the side of the trail, there to wait and catch his pursuer as he passed. So Olear sidled into the all but impenetrable underbrush and slowly, with infinite caution, wormed his way along.

Presently he came to the little rise of ground where Morones had disappeared, but a painstaking search did not reveal the factor. There were, however, a number of other trails that joined the very faint trail he had been following, and now there was a well-defined track which continued to lead upward. With a grimace of disgust Olear again plunged into the odorous underbrush and traveled parallel to the trail. It was well he did so, for several Mercurians passed swiftly, intent, so it seemed, in answering a shrill call that at times came faintly to the ear. They carried slender spears.