"We are going to leave Havatoo forever," I replied, and just then I saw a car pass us and draw up in front of the house we had just left. Two men were in it; one of them jumped out and ran to the door; then I opened the throttle. I had seen enough to turn me cold with apprehension. Duare had seen, too. "Now they will discover everything," she said, "and you will be killed. I knew that it would end in disaster. Oh, why didn't you let me die alone? I want to die." "But I won't let you!" She said nothing more, and we sped through the now almost deserted streets of Havatoo toward the Kantum Lat and the Gate of the Physicists. We had gone about two miles of the three that we must cover before we reached our destination when I heard an ominous sound such as I had never before heard in Havatoo. It sounded like the wailing of sirens such as are used on police cars in the large cities of America. Instantly I knew that it was an alarm, and I guessed that the man who had entered the house of Hara Es had discovered her and that our escape was known. Closer and closer came the sounds of the wailing sirens as I drew up before the hangar where my plane stood; they seemed to be converging upon us from all directions. I was not surprised that they should have guessed where they would find us, for it would have been obvious to even duller minds than those of Havatoo that here lay my only chance to escape. Fairly dragging Duare with me, I leaped from the car and ran into the hangar. The great doors, operated by mechanical means, rolled open at the touch of a button. I lifted Duare into the cockpit. She asked no questions; there was no time for questions. Then I took my place at her side. I had designed the plane for training purposes; and it had two seats, each accommodating two people. I started the motor--and such a motor! Silent, vibrationless, and it required no warming up. I taxied out into the Kantum Lat. The sirens were very close now. I saw the lights of cars bearing down upon us. As I started toward the Gate of the Physicists I heard the staccato hum of Amtorian rifles behind us. They were firing at us! I nosed up; the wheels left the ground; the great gate loomed directly ahead. Up! Faster! Faster! I held my breath. Would we make it? Responding perfectly, the light ship climbed almost vertically in the last few seconds; she sped over the top of the lofty gate with only inches to spare. We were safe! Far below, the lights of Havatoo lay behind us as I turned the ship's nose toward the shimmering ribbon that was the River of Death--the River of Life to us--that was to guide us down to that unknown sea where, I was confident, we would find Vepaja. Duare had not spoken. I felt her arm against mine trembling. I reached over and laid a hand upon it. "Why are you trembling?" I asked. "You are quite safe now." "What is this thing we are in?" she asked. "Why does it not fall to the ground and kill us? What keeps it up?"