Far below them, in a ravine, a cylindrical building was now visible, and toward this the car began to drop. It landed on a level space before the structure. A sliding gate opened, and the car wheeled into a sort of courtyard, protected from the cold of night by an arching roof of glass. Sime was hustled out and led into an office located on the lower floor of the fortification, or whatever the structure was. As he saw the man who sat at the desk he gave a startled explanation. "Colonel Barkins!" * * * * * The elderly, white-haired man smiled. He brushed back his hair with a characteristic gesture, and his twinkling blue eyes bored into those of the I. F. P. special officer. The colonel wore the regular uniform of the service; his little skullcap, with the conventionalized sun symbol denoting his rank, was on the table before him. He put out his lean, strong hand. "Surprised to see me, eh, Hemingway?" he inquired pleasantly. Sime managed an awkward salute. "I don't quite understand, sir. You gave me my instructions at the Philadelphia space port just before I made the _Pleadisia_. She's the fastest passenger liner in the solar system: I've barely landed here, and it seems you got here before me. It don't seem right!" Sime watched the colonel narrowly, a vague suspicion in his mind, and he thought he saw a slight flicker in the man's eye when Sime spoke. But the colonel answered smoothly, with a hint of reproof. "Never mind questioning me now, Hemingway. The mission is important. I want to know if you remember every detail of what I told you." He nodded to the men, and they filed out of the room. "Repeat your orders." "Nothing doing, Colonel!" Sime replied promptly and respectfully. "In fact, Colonel, you can go to hell! This is the first time that a man of the I. F. P. has turned traitor, and if your men hadn't so thoughtfully taken my neuro I'd be pleased to finish you right now!" "But you observe I have a neuro in my hand," remarked the colonel pleasantly, "and so you will remain standing where you are." * * * * * So saying, he slipped off the white wig he was wearing, wiped his face so that the brown powder came off, and sat, obviously pleased with the success of his masquerade, useless though it was. He was a typical Martian, dark, sleek-haired, coral-skinned. "I hate to send a man to his death mystified," said the Martian after a moment, "so I'll explain that I am Scar Balta!" "Scar Balta!" "You've heard of me?" "Uh--yes and no," Sime suddenly remembered the girl of the evening before--the imperious little Martian. She had warned him of Scar Balta. "If I do say it," said the Martian, "I am the best impersonator in the service of the interests I represent. I did not expect to get information of great value from you, but we do not neglect even the most unpromising leads." He pressed a button; two Martian soldiers answered promptly.