_When the final problem of communicating with a ship in space was solved, the laboratories on Venus Equilateral returned to their original trends. These lines of research and study were wide and varied. Men dabbled brilliantly with insane, complex gadgets that measured the work-functions of metals in electron emission and they made conclusive measurements on the electrical conductivity under extremes of heat and cold. From the uranium pile that powered Venus Equilateral there came metals that had been under neutron bombardment long enough to have their crystal structure altered in unfathomable ways. These were investigated by men who toyed with them to ascertain whether or not they possessed any new properties that might make them useful. Many were the fields studied, too, because it is often that a chemist may be baffled by a problem that could be solved by a thorough education in electronics, for instance._ _And from the diversified studies and researches there often came strange by-products. The quick leap of the physicist from a hare-brained theory to a foregone conclusion has been the subject of laughter, but it is no less related than the chain of events that led from an exposed photographic plate to Hiroshima._ _Or the chain of events that led Wes Farrell from his observation of a technician cleaning up a current-sputtered knife switch to a minor space war...._ FIRING LINE Mark Kingman was surprised by the tapping on his window pane. He thought that the window was unreachable from the outside--and then he realized that it was probably someone throwing bits of dirt or small stones. But who would do that when the doorway was free for any bell-ringer? He shrugged, and went to the window to look out--and became crosseyed as his eyes tried to cope with a single circle not more than ten inches distant. He could see the circle--and the lands on the inside spiralling into the depths of the barrel--and a cold shiver ran up his spine from there to here. Behind the heavy automatic, a dark complected man with a hawklike face grinned mirthlessly. Kingman stepped back and the stranger swung in and sat upon the windowsill. "Well?" asked the lawyer. "Is it well?" asked the stranger. "You know me?" "No. Never saw you before in my life. Is this a burglary?" "Nope. If it were, I'd have drilled you first so you couldn't describe me." Kingman shuddered. The stranger looked as though he meant it. "In case you require an introduction," said the hard-faced man. "I'm Allison Murdoch." "Hellion?" "None other." "You were in jail--" "I know, I've been there before." "But how did you escape?"