Ross sat up quickly, a question in his staring eyes. "You mean--the way the red stars go dim when we drain them of the red rays that power our ships and inter-planet communications?" "Just that way," said Moore, blinking in excitement. For a long moment their glances were locked. Then Ross heaved a stifled sigh. "This may mean a lot, Harry," he murmured. "I wonder if it might not even mean--" "Whatever happened to Number Eight?" asked Moore quickly. Slowly Ross nodded. "Let's see. Denabola's a blue star. Have you checked on any other blue stars?" Moore took the seat at the star scope. "Only Vega. She's dim, too. Let me get Sirius." He twirled a knob at the side of the telescope barrel, then another, then straightened, with an explosive gasp. "Look at Sirius!" Ross looked and caught his breath. Sirius, the brightest star in all the firmament, was a dull lackluster thing. Flight-Commander Bruce Ross sat back at the star-scope and pushed his space helmet off his head. He ran a steady hand through his unruly blond hair, smoothing out the tight wrinkles in his broad forehead as if to silence the urgent question that hammered in his brain. Something was happening in the heavens, and all his lore of flying and fighting might be none too much to set against the celestial puzzle. "Harry," he asked finally, "the Moon Men know all about our red-ray work. Do you suppose they've gone to work somehow on the blue stars?" Moore screwed up his face, blinking behind his glasses. "Well," he said finally, "there's Horta." Ross nodded. "I was thinking of Horta," he admitted grimly. He had never forgotten Horta, Lord of the Moon Caverns, the darkly hostile savant who had held out so long at that fateful conference when the Council of Seven, rulers of the Earth, had made their all-or-nothing flight to the Moon, there to lay the question of peace or war before Magnus, the Moon King, and his lords. The Seven had won Horta over finally by offering him all the Earth secrets of the red rays that had made Earth-Moon travel possible. They had even set up a ray reservoir in Horta's great cavern, and had shown him how the harnessed rays could provide power for ships and explosive for sky-torpedoes. Yet Horta had never succeeded in building any but tiny ships that could barely circle the Moon, and he had denied any success with the torpedoes. Only on the ray-type and the ray-phone, essential to Earth-Moon intercourse, had he followed instructions with real results. * * * * * "Blue rays, then?" muttered Ross, staring at Moore. He turned as Jorgens appeared hesitantly. "Well?" "Garbled message by ray-phone from our Earth station, sir. From Censor Trowbridge, apparently." Jorgens handed over a sheet of paper. "We put it down as we heard it." Ross and Moore bent over it eagerly. "... trouble ... Moon ... Four ... Magnus killed...." It ended with "... bridge." Ross wheeled on Jorgens. "Magnus--killed? Is that what you heard?"