Free The Space Trilogy by Arthur C. Clarke

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    Besides the spaceships on the regular, scheduled runs, about two or three times a month ships on special missions touched at the Station. Usually they were engaged on scientific research, occasionally something really exciting like an expedition to the outer planets. Whatever it was they were doing, everyone aboard the Station always knew all about it.
    But no one knew much about the Cygnus , except that she was down in Lloyd's Register as a medium freighter, and was about due to be withdrawn from service since she had been in operation for almost five years without a major overhaul. It attracted little surprise when she came up to the Station and anchored (yes, that's the expression still used) about ten miles away. This distance was larger than usual, but that might only mean that she had an ultra-cautious pilot. And there she stayed. All attempts to discover what she was doing failed completely. She had a crew of two—we knew that because they jetted over in their suits and reported on Control. They gave no clearance date and refused to state their business, which was unheard of but not illegal.
    Naturally this started many theories circulating. One was that the ship had been chartered secretly by Prince Edward, who as everybody knew had been trying to get out into space for years. It seems the British Parliament wouldn't let him go, the heir to the throne being considered too valuable to risk on such dangerous amusements as space-flight. However, the Prince is such a determined young man that no one will be surprised if he turns up on Mars one day, having disguised himself and signed on with the crew. If he ever tries anything like this, he'll find plenty of people ready to help him.
    But Peter, of course, had a much more sinister theory. The arrival of a mysterious and untalkative spaceship fitted in perfectly with his ideas on inter-planetary crime. If you wanted to rob a space-station, he argued, how else would you set about it?
    We laughed at him, pointing out that the Cygnus had done her best to arouse suspicion rather than allay it. Besides, she was a small ship and couldn't carry a very large crew. The two men who'd come across to the Station were probably all she had aboard.
    By this time, however, Peter was so wrapped up in his theories that he wouldn't listen to reason, and because it amused us we let him carry on, and even encouraged him. But, of course, we didn't take him seriously.
    The two men from the Cygnus would come aboard the Station at least once a day to collect any mail from Earth and to read the papers and magazines in the rest room. That was natural enough, if they had nothing else to do, but Peter thought it highly suspicious. It proved, according to him, that they were reconnoitring the Station and getting to know their way around. 'To lead the way, I suppose,' said someone sarcastically, 'for a boarding-party with cutlasses.'
    Then, unexpectedly, Peter turned up fresh evidence that made us take him a little more seriously. He discovered from the Signal Section that our mysterious guests were continually receiving messages from Earth, using their own radio on a waveband not allocated for official or commercial services. There was nothing illegal about that—they were operating in one of the 'free ether' bands—but once again it was distinctly unusual. And they were using code. That, of course, was very unusual, to say the least. Peter was naturally very excited at all this. 'It proves that there's something funny going on,' he said belligerently. 'No one engaged on honest business would behave like this. I won't say that they're going in for something as—well, old-fashioned—as piracy. But what about drug smuggling?'
    'I should hardly think,' put in Tim Benton mildly, 'that the number of drug addicts in the Martian and Venusian colonies would make this very profitable.'
    'I wasn't thinking of smuggling in that direction,' retorted Peter scornfully. 'Suppose someone's discovered a drug on