They stepped out onto a ledge which extended perhaps a hundred yards, then dropped sheerly away. The walls curving up were of polished smoothness, and stretched away into unimaginable distances. The soft bluish light came from these walls and seemed to pervade the whole interior of this hollow world. The air was damp but comfortably warm. And the gravity.... Praana clutched at Tal Horan's arm. "This is almost Mars gravity! But ... where do they get it?" "Yes, we'll have to look into that later." Tal cautioned her to silence. A three-wheeled car was waiting for them. Kueelo hurried them into it, and Naric took the controls. Soon they were speeding away, and they gasped as their ledge tapered off into nothingness! They were traversing the inside of the shell itself. "It's eerie at first," Kueelo told them, "but you'll soon become accustomed to our gravity. Just imagine the space out there as being _up_. The only difference is that our light comes from the surface instead of overhead." "What's the interior diameter?" Ric gestured outward. "About three hundred miles. And you were wondering about our gravity, Tal Horan? It comes from out there!" Kueelo gestured vaguely at the gray-blue interior. "Our power plant is anchored in space at the exact center of Phobos. But it's reverse gravity--that is to say, its force extends _outward_ toward the shell, instead of pulling inward." Tal saw that the man was communicative. He nodded thoughtfully. "Quite an engineering feat! It must have taken a long time to set up all this!" "Two generations! It was not done in my time." "Where are we going now?" "To the city of the Phobians." Praana gasped. "Native Phobians? But there are no Phobians left! For three hundred years--" "That's the popular supposition, and it suits our convenience. Yes, three hundred years ago the war between Mars and Phobos was supposed to have ended. But you shall see! Perhaps Gorak himself will have much to tell you." "Gorak?" "The present Phobian leader! There are only a few thousand Phobians remaining, as there are only a few thousand of your people. Ironic, is it not ... Princess Praana?" * * * * * The city came into view, a sheer grotesquerie of impossible buildings jutting crazily into space. However, as they came nearer, it was apparent that many of them were abandoned. They passed through a long street and entered a building which Kueelo seemed to know well. He was familiar with everything here, Ric thought--too familiar! They came into a room where a man sat at a table, poring over charts and figures. He looked up, greeted Kueelo and Naric by name. "This is Tal Horan, and the Princess Praana!" Kueelo said, the pride of accomplishment in his voice. "We have done better than we supposed! And this one is Ric Martin, who foolishly came into space to warn Dar Mihelson."