The entire wall swung around on pivots. A blast of foul air struck him. Ketrik stepped into a small passage. He recognized it as one of the underground sewers of Turibek. He followed it and came to a short flight of stone stairs leading up to a hinged door. Slowly he shoved it open. He was in Turibek! This was one of the narrow, winding streets in the warehouse district. He glanced at the sky. It was night. Deimos was gone below the horizon, but Phobos rode high on liquid sapphire. Ketrik rested there for a few hours until Phobos descended. Then, in the utterly dark hour that precedes dawn on Mars, he crept forth and sought the shop of one Jal Thurlo in the Street of the Double Moon. IV He found the shop, in a twisting little street that seemed to cringe from the rest of the city. The insignia of Jal Thurlo was still upon the door, and Ketrik breathed a sigh of relief. Finally, after his persistent knocking, the door opened a trifle and Ketrik saw the wizened little face of Jal Thurlo. The shop-keeper's eyes were dark with suspicion. "I was told I would find one Jal Thurlo here," Ketrik said glibly. "I come with news of a secret shipment. Rare _kaladonis_ furs from the plains of Io." "At this ungodly hour?" Thurlo grumbled sleepily. "It is the proper hour for such matters, thou sulky one! Permit me to enter now or I take my news elsewhere!" Thurlo opened the door, and Ketrik slipped into a dark room that smelled of spices, perfumes, and a miscellany of objects from the far planets. He followed the little Martian through the shop and along a dim corridor, until they arrived at the living quarters. There, under brilliant light, Thurlo faced him. "Who sent you?" Ketrik answered carefully. He knew this little man carried a needle-gun in his sleeve and had used it on occasion. "No one. I merely seek haven here. I once saved your life on Deimos--you remember it?" Thurlo started visibly. "Ketrik! Is it really you? But no, it cannot be!" "It's Ketrik, all right. But 'Khosan' for the time being. Remember this?" He bared one arm and revealed a long jagged scar from shoulder to elbow. He further proved his identity by recounting the adventure on Deimos many years ago, in which he'd received this scar while saving Thurlo's life. "I must remind you of the Martian blood debt," he ended. "I saved your life and it is forfeit to me until you repay." "I have not forgotten!" He looked at the other's torn and bleeding legs. "Come, man, let me dress those wounds! Then you can tell me why you are here." Ketrik recounted part but not all. When he had finished, impressing upon Thurlo the urgent need to get inside Dar Vaajo's laboratories, the little Martian shook his head.