As he climbed out of the airlock, there again came the sensation of vertigo which he felt every time he stood on this island suspended in nothingness. The circumference of the doughnut stretched its great arc away from him in both directions, while twelve miles away, at the center of the circle, was the spherical shape of the radiotelescope receiver. The long, slender girders which bound the station together had a fragile, spidery appearance. Britten and Glover walked clumsily to the linear accelerator which projected one-billion-volt protons into the initial lap of their long journey around the doughnut. At the far end of the hundred-foot tube, within a shielded chamber, was the glass bottle of the ion source. Normally, a brilliant crimson flame glowed within this bottle as numberless protons were stripped from their electrons, to be hurled down the accelerator tube. Now there was nothing but the blackened, dead glass. As they approached the chamber that surrounded the ion source, Britten found that the resentment left over from the previous night had a new object upon which to fasten. Why should he be doing the work that belonged to the technicians? In his anger he lost sight of the fact that Professor Glover was out there doing the same thing. Damned slave labor, he thought. A PhD candidate was at the bottom of the heap, the lowest form of existence, pushed around by everybody else. Glover thought he was being clever, pushing him off the project, making excuses about security, when probably his aim was to keep for himself the Nobel Prize that the experiment was going to receive some day. Thought he could keep his poor stupid student in the dark about the outcome of the experiment--but the poor student wasn't as stupid as he thought. Glover reached the hatch that opened into the ion-source chamber and started undoing the fastenings. Suddenly he turned and stared at Britten. "Where's the new ion source?" he snapped. "Don't tell me you left it in the airlock!" Britten stammered wordlessly, shocked out of his reverie. "Well, of all the stupid--Go back and get it! I'll remove the old source." Glover turned his back and continued to unfasten the hatch. Rage came into full bloom instantly. Without an instant's thought, Britten reached out both hands, wrenched the antenna rod from Glover's back, tore his anchoring lines from their snaps, and pushed the struggling body out into space, where it soon dwindled away into a tiny speck. CHAPTER II Dr. Morris Wolf leaned back in his chair after Jim Britten was wheeled, asleep, from the therapy room. In a random fashion he let his mind wander over the story he had just heard, savoring not only the facts, but the feelings behind them and the intuitions which they built up in his own mind. "Well, Alma, what do you think?" he said, swiveling his chair to look at the other doctor across his desk.