A little cloud of riding-lights swept toward the dome from an infinite distance away. Darkness was falling so swiftly that they were still merely specks of light as they swept up to and seemed to melt into the swirling, swooping mass of fliers about the dome.... Cold sweat was standing out on Thorn's face, despite the violence of his exertions. He was even praying a little.... And suddenly the searchlight beam flickered a welcome answer: "W-e u-n-d-e-r-s-t-a-n-d. R-e-p-o-r-t." Thorn flung his arms about madly, sending: "G-e-t a-w-a-y q-u-i-c-k. C-o-m P-u-b-s h-e-r-e. W-i-l-l m-a-k-e o-t-h-e-r d-o-m-e o-u-t-s-i-d-e t-o t-r-a-p y-o-u." The searchlight beam upon him flickered an acknowledgment. He knew what was happening after that. The G.C. phones would flash the warning to every ship, and every ship would dash madly for safety.... A sudden, concerted quiver seemed to go over the whirling maze of lights aloft. A swift, simultaneous movement of every ship in flight. Thorn breathed an agonized prayer.... There was a flash of blue light. For one fractional part of a second the stars and skies were blotted out. There was a dome of flame above him and all about the world, of bright blue flame which instantly was--and instantly was not! Then there was a ghastly blast of green. Hexynitrate going off. In this glare were silhouetted a myriad motes in flight. But there was no noise. A second flare.... And then Thorn Hard, groaning, saw flash after flash after flash of green. Monster explosions. Colossal explosions. Terrific detonations which were utterly soundless, as the ships of the Fighting Force, in flight from the menace of which Thorn had warned them, crashed into an invisible barrier and exploded without cracking it. * * * * *