"Yes, I have just arrived. I am a buyer for Varik's." He saw the man was impressed. "I find Turibek a fascinating city, but tell me--the high wall to the east of here--what is it? They would not allow me to pass!" "And no wonder, sir. Those walls surround the palace grounds and laboratories of our Emperor!" "To be sure! I should have known that." Ketrik smiled, and when he spoke again there was the slightest hint of mockery. "Ah, but you of Turibek should be flattered that our Emperor chose your city to carry on his noble experiments." The man hesitated, glanced around, but decided to speak. "I think you know we are not fortunate, sir. What Dar Vaajo is doing may be for the best ... but if only we were informed!" Ketrik raised his brows in puzzlement, and the other went on, "Eh, then you do not know of it? But of course not--you have just arrived. Well, sir, it is to come again _tonight_--at two hours past the midnight. This morning's Tele-news warned all residents to stay in their homes at that hour--and we know what that means." * * * * * Ketrik knew, too. The green radiance which Thurlo had spoken of. Tonight! He wanted to observe that display! Then he thought of the Rajecs, the caravan of two hundred which had just that day entered the city. His mind leaped. Was it mere coincidence, that upon this very day...? He said carelessly, "I have heard that more of those wretched Rajecs were permitted entrance this morning. It seems a stupid thing, this treaty which allows the outlanders to pollute our cities!" "It would seem so, yes. But Dar Vaajo is cunning in his way. Perhaps the blacks are shipped north, to work the Uranium mines!" Ketrik dared ask no more questions. He left the shop and continued his stroll toward the wall. When he came within a block of it he could see that it wasn't stone, as he had supposed. It was heavy mesh-_duraplon_ reaching twenty feet high, and still higher were the electronic control-towers. A touch of a button would throw any section of this wall into flaming, deadly radiance. Here was a formidable barrier! Ketrik frowned, looking at it--but he didn't dare linger there too long. He turned back, was crossing the street when he heard a warning shout and then a clarion-blast. He leaped to the curb just as a vehicle swept by. It swerved sharply to avoid hitting him. Two others followed--they were the three-wheeled, electronic-powered cars native to Mars. From the rear seat of the second car a girl's face peered out, a bit frightened at the near accident. A golden face, lovely, with copper-hued hair tumbling in waves to her shoulders, and eyes large and blue as _asterines_. This much Ketrik saw, before the cars were gone. He turned and stared. A section of the _duraplon_ wall slid upward and the cars passed through; all, except the last one. It turned sharply and came hurtling back to where Ketrik stood. A pompous Martian climbed out, strode angrily up to him.