The miniature menace

A THRILLING NOVELET
Condemned without trial for his refusal to open fire on an alien space-craft, Ralph Langford had to be free to investigate the strange menace from beyond the stars! For if the alien were an enemy, then it would be the most terrible enemy men had ever encountered.
The sky was harsh with the flare of rocket jets when Captain Ralph Langford emerged from his deep space cruiser on the Mars City landing field. There was a girl standing alone at the far end of the field, and for a moment Langford thought it might be Joan, irrational as the thought was. Of course, Joan couldn't be here; he was to see her at the hospital. He started across the field, blinking in the glare, his eyes shining with a warm gratefulness to be home again; as he approached the solitary figure, he could see it was not Joan, though there was a resemblance. He was so engrossed that he didn't notice the tall, eagle-eyed young Patrol officer who came striding toward him, until he heard the man's voice.
You're under arrest, sir! the youth said, his hand whipping to his visor. Commander Gurney's orders.
Langford looked up suddenly, then stiffened in belligerent protest. Hold on, Lieutenant! You can't arrest me and march me off to jail like a common criminal. Commission regulations! How long have you worn those stripes, youngster?
The youth's eyes were respectful, sympathetic; he did not appear to be offended. I'm sorry, sir, he said firmly. Commander Gurney went before the Commission and had you certified as irresponsible.
Langford flushed angrily. So that's it, he grunted.
The Patrol officer hesitated. He had prepared what he intended to say, but the fame of the big man facing him had reached sunward to Mercury, and outward to Pluto's frozen tundras.
Langford's fist lashed out suddenly, catching the youth flush on the jaw, and crumpling him to his knees. The girl, who had been a silent witness up to now, gasped, then turned and ran like a frightened rabbit. Langford did not stop to apologize. Rumor had it that deep space officers bore charmed lives, but Langford knew as he broke into a run that his life hung by a thread that might at any moment turn crimson.