A World is Born, Leigh Brackett, Comet, July 1941. Note: The copyright for this story has expired in the United States and, thus, now resides in the public domain. 

The ship was a commercial job, fairly slow but sturdy. Gray strapped Jill Moulton into one of the bucket seats in the control room and then checked the fuel and air gauges. The tanks were full.
"What about you?" he said to Ward. "You can't go back."
"Nah. I'll have to go with you. Warm her up, Duke, while I open the dome."
He darted out. Gray set the atmosphere motors idling. The dome slid open, showing the flicker of the auroras, where areas of intense heat and cold set up atmospheric tension by rapid fluctuation of adjoining air masses.
Mercury, cutting the vast magnetic field of the Sun in an eccentric orbit, tortured by the daily change from blistering heat to freezing cold in the thin atmosphere, was a powerful generator of electricity.
Ward didn't come back.
Swearing under his breath, tense for the sound of pursuit in spite of the girl, Gray went to look. Out beyond the hangar, he saw a figure running.
Running hard up into the narrowing cleft of the valley, where natural galleries in the rock of Mercury led to the places where the copper cables were anchored, and farther, into the unexplored mystery of the caves.
Gray scowled, his arrogant Roman profile hard against the flickering aurora. Then he slammed the lock shut.
The ship roared out into the tearing winds of the plain. Gray cut in his rockets and blasted up, into the airless dark among the high peaks.
Jill Moulton hadn't moved or spoken.
Gray snapped on the space radio, leaving his own screen dark. Presently he picked up signals in a code he didn't know.
"Listen," he said. "I knew there was some reason for Ward's running out on me."
His Indianesque face hardened. "So that's the game! They want to make trouble for you by letting me escape and then make themselves heroes by bringing me in, preferably dead.
"They've got ships waiting to get me as soon as I clear Mercury, and they're getting stand-by instructions from somebody on the ground. The somebody that Ward was making for."
Jill's breath made a smill hiss. "Somebody's near the Project...."
Gray snapped on his transmitter.
"Duke Gray, calling all ships off Mercury. Will the flagship of your reception committee please come in?"
His screen flickered to life. A man's face appeared--the middle-aged, soft-fleshed, almost stickily innocent face of one of the Solar Systems greatest crusaders against vice and crime.
Jill Moulton gasped. "Caron of Mars!"
"Ward gave the game away," said Gray gently. "Too bad."
The face of Caron of Mars never changed expression. But behind those flesh-hooded eyes was a cunning brain, working at top speed.
"I have a passenger," Gray went on. "Miss Jill Moulton. I'm responsible for her safety, and I'd hate to have her inconvenienced."
The tip of a pale tongue flicked across Caron's pale lips.
"That is a pity," he said, with the intonation of a preaching minister. "But I cannot stop the machinery set in motion...."
"And besides," finished Gray acidly, "you think that if Jill Moulton dies with me, it'll break John Moulton so he won't fight you at all."
His lean hand poised on the switch.
"All right, you putrid flesh-tub. Try and catch us!"
The screen went dead. Gray hunched over the controls. If he could get past them, lose himself in the glare of the Sun....
He looked aside at the stony-faced girl beside him. She was studying him contemptuously out of hard gray eyes.
"How," she said slowly, "can you be such a callous swine?"
"Callous?" He controlled the quite unreasonable anger that rose in him. "Not at all. The war taught me that if I didn't look out for myself, no one would."
"And yet you must have started out a human being."
He laughed.
The ship burst into searing sunlight. The Sunside of Mercury blazed below them. Out toward the velvet dark of space the side of a waiting ship flashed burning silver.
Even as he watched, the flare of its rockets arced against the blackness. They had been sighted.
Gray's practised eye gauged the stranger's speed against his own, and he cursed softly. Abruptly he wheeled the ship and started down again, cutting his rockets as the shadow swallowed them. The ship was eerily silent, dropping with a rising scream as the atmosphere touched the hull.
"What are you going to do?" asked Jill almost too quietly.
He didn't answer. Maneuvering the ship on velocity between those stupendous pinnacles took all his attention. Caron, at least, couldn't follow him in the dark without exhaust flares as guides.
They swept across the wind-torn plain, into the mouth of the valley where Gray had worked, braking hard to a stop under the cables.
"You might have got past them," said Jill.
"One chance in a hundred."
Her mouth twisted. "Afraid to take it?"
He smiled harshly. "I haven't yet reached the stage where I kill women. You'll be safe here--the men will find you in the morning. I'm going back, alone."
"Safe!" she said bitterly. "For what? No matter what happens, the Project is ruined."
"Don't worry," he told her brutally. "You'll find some other way to make a living."
Her eyes blazed. "You think that's all its means to us? Just money and power?" She whispered, "I hope they kill you, Duke Gray!"
-- -- -- -- -- -- -- -- -- --
He rose lazily and opened the air lock, then turned and freed her. And, sharply, the valley was bathed in a burst of light.
"Damn!" Gray picked up the sound of air motors overhead. "They must have had infra-red search beams. Well, that does it. We'll have to run for it, since this bus isn't armed."
With eerie irrelevancy, the teleradio buzzed. At this time of night, after the evening storms, some communication was possible.
Gray had a hunch. He opened the switch, and the face of John Moulton appeared on the screen. It was white and oddly still.
"Our guards saw your ship cross the plain," said Moulton quietly. "The men of the Project, led by Dio, are coming for you. I sent them, because I have decided that the life of my daughter is less important than the lives of many thousands of people.
"I appeal to you, Gray, to let her go. Her life won't save you. And it's very precious to me."
Caron's ship swept over, low above the cables, and the grinding concussion of a bomb lifted the ship, hurled it down with the stern and twisted to uselessness. The screen went dead.
Gray caught the half stunned girl. "I wish to heaven I could get rid of you!" he grated. "And I don't know why I don't!"
But she was with him when he set out down the valley, making for the cliff caves, up where the copper cables were anchored.
Caron's ship, a fast, small fighter, wheeled between the cliffs and turned back. Gray dropped flat, holding the girl down. Bombs pelted them with dirt and uprooted vegetables, started fires in the wheat. The pilot found a big enough break in the cables and came in for a landing.
Gray was up and running again. He knew the way into the explored galleries. From there on, it was anybody's guess.
Caron was brazen enough about it. The subtle way had failed. Now he was going all out. And he was really quite safe. With the broken cables to act as conductors, the first thunderstorm would obliterate all proof of his activities in this valley. Mercury, because of its high electrical potential, was cut off from communication with other worlds. Moulton, even if he had knowledge of what went on, could not send for help.
Gray wondered briefly what Caron intended to do in case he, Gray, made good his escape. That outpost in the main valley, for which Ward had been heading, wasn't kept for fun. Besides, Caron was too smart to have only one string to his bow.
Shouts, the spatter of shots around them. The narrow trail loomed above. Gray sent the girl scrambling up.
The sun burst up over the high peaks, leaving the black shadow of the valley still untouched. Caron's ship roared off. But six of its crew came after Gray and Jill Moulton.
-- -- -- -- -- -- -- -- -- --
The chill dark of the tunnel mouth swallowed them. Keeping right to avoid the great copper posts that held the cables, strung through holes drilled in the solid rock of the gallery's outer wall, Gray urged the girl along.
The cleft his hand was searching for opened. Drawing the girl inside, around a jutting shoulder, he stopped, listening.
Footsteps echoed outside, grew louder, swept by. There was no light. But the steps were too sure to have been made in the dark.
"Infra-red torches and goggles," Gray said tersely, "You see, but your quarry doesn't. Useful gadget. Come on."
"But where? What are you going to do?"
"Escape, girl. Remember? They smashed my ship. But there must be another one on Mercury. I'm going to find it."
"I don't understand."
"You probably never will. Here's where I leave you. That Martian Galahad will be along any minute. He'll take you home."
Her voice came soft and puzzled through the dark.
"I don't understand you, Gray. You wouldn't risk my life. Yet you're turning me loose, knowing that I might save you, knowing that I'll hunt you down if I can. I thought you were a hardened cynic."
"What makes you think I'm not?"
"If you were, you'd have kicked me out the waste tubs of the ship and gone on. You'd never have turned back."
"I told you," he said roughly, "I don't kill women." He turned away, but her harsh chuckle followed him.
"You're a fool, Gray. You've lost truth--and you aren't even true to your lie."
He paused, in swift anger. Voices the sound of running men, came up from the path. He broke into a silent run, following the dying echoes of Caron's men.
"Run, Gray!" cried Jill. "Because we're coming after you!"
The tunnels, ancient blowholes for the volcanic gases that had tortured Mercury with the raising of the titanic mountains, sprawled in a labyrinthine network through those same vast peaks. Only the galleries lying next the valleys had been explored. Man's habitation on Mercury had been too short.
Gray could hear Caron's men circling about through connecting tunnels, searching. It proved what he had already guessed. He was taking a desperate chance. But the way back was closed--and he was used to taking chances.
The geography of the district was clear in his mind--the valley he had just left and the main valley, forming an obtuse angle with the apex out on the wind-torn plain and a double range of mountains lying out between the sides of the triangle.
Somewhere there was a passage through those peaks. Somewhere there was a landing place, and ten to one there was a ship on it. Caron would never have left his men stranded, on the off chance that they might be discovered and used in evidence against him.
The men now hunting him knew their way through the tunnels, probably with the aid of markings that fluoresced under infra-red light. They were going to take him through, too.
They were coming closer. He waited far up in the main gallery, in the mouth of a side tunnel. Now, behind them, he could hear Dio's men. The noise of Caron's outfit stopped, then began again, softly.
Gray smiled, his sense of humor pleased. He tensed, waiting.