Charleston harrrrumphed again but reached out to switch on the receiver. Immediately he started receiving the steady hum of the on-course signal, broken at 30 second intervals by the keying of P V, identification signal of the base station. A minute later he heard the dash-dot signifying N, meaning that he was to the left (and in his case presumably to the north) of his course. Keying in the port jets he swung to the right and received the on-course signal again. He noticed with satisfaction that the destroyer had done likewise. "Ginny," he admitted weakly, "this radio range business is quite _the_ business. Of course the Charleston infrareds--" "_Of course!_" smiled the daughter. It was Charleston's turn to be squelched. Suddenly the range signals were interrupted by the beam operator's voice: "PV, Pali-Vanyi. Notice to all spacemen. Due to the unusually adverse weather conditions at surface, the north-south landing beams will be left on permanently until further notice. PV, Pali-Vanyi." Ten minutes had passed since Ward had begun rotating the goniometer. Ten minutes and Charleston and the destroyer were fifty degrees off the true course. Almost south-south-west of the field now and gradually bearing more to the south. But Charleston did not know and he was praising the facilities of the Authority and remarking about how wonderfully his infrareds would work in conjunction with said facilities. The future of his invention (well, he had backed it!) took on a rosy hue. He would revolutionize interplanetary travel; he would simply make it easier. V Slowly Silvy Ward rotated the flat, indexed dial of the goniometer. Eighty-nine degrees gone. One more degree. The destroyer should be at the south of the field now, coming in unknowingly over the blacked-out metropolis. Soon he should hear the thunder of its rockets. Were his computations wrong? Did the destroyer have improved compasses and other directional finding instruments which it was using instead of relying on the beam? If not, why did he not hear it coming out of-- A chill swept over him. What was that far, thin thunder throbbing across the night? The destroyer! And that other, higher pitched roar? The Patrol had said that there were two unlisted ships coming in! Who was in that other ship? If he could only warn them without the destroyer catching the signal! But, dear God, he couldn't! Zero-one-two-zero! Over against the Hump Portiz was attending the portable landing beam transmitter. An ultra-high frequency beam was shooting up uni-directionally at the glide angle of a ship coming in for a landing from the west. A normal landing was to the south where the main runways lay; this descent--no landing there!--must be to the east and the five thousand foot Hump along whose base the boundary lights were ablaze in the dense fog. From the air they would present the aspect of an illumined city.... Ward cried out to Wagner: