"Seventy-three milliseconds is the best we've been able to clock. That's a close screen, and it takes considerable stability in the generators to hold it. The best barriers for distance and power establish in point one nine eight seconds. Anything beyond that would require too much holding power, anything closer requires more generator stability." "How does instability affect the screen?" "Won't hold up. It collapses, and the build-up begins from zero again. That would be dangerous." "You've been a busy boy," smiled Kane. "Also a definite credit to us all." "Thanks." "And how do you intend to operate this thing in practice?" asked Kane. "Not attack, in defense. I mean?" "We've got the thing hitched to the finders," Maynard punched a switch. "Now, for instance, if anything that radiates comes within detector range of us, the barrier goes on. You'll see that everything is tacked down. We've been trying it out with the tenders, and the first time we did it, we went free and everything floated around the place in no-gravity. We're now protected, and if your pilot should kick his drive, we'd go free." Maynard adjusted three dials. "Now," he said, "the spotter is set to neglect any radiation from the _Loki_. We can set up many such channels, compensating for every ship in a flight, and yet have the whole flight protected in case of intrusion by another ship." "You've got everything all set, haven't you?" "Just about. If we had torpedoes, we could declare a private war on Mars." "Then you're about finished?" "Just about. Want to come in with us, or will you go in the _Loki_?" "I'll ride with you, if you do not mind." "Not at all," smiled Guy. "Executive to Communications: Inform _Loki_ that Kane will return with us, and to make for Terra immediately." "Check." "We'll lose him," grinned Guy. "We're all set for 5-G." "He'll take it easy, at three. I don't mind." "Executive to Pilot: Take course for Terra at five!" "Check!" * * * * * The _Asterite_ turned and left the _Loki_ far behind, and the velocity began to build up for the return trip. An hour later, with the _Asterite_ bettering a hundred miles per second, the second incident occurred. It came as a complete surprise, since they were running through a restricted space, and Maynard remarked that it looked more like a public thoroughfare. The finder-alarm clanged stridently, and immediately the ship went free. Men clutched at the hand-rails, and as they settled down, the technician took the communicator and started to speak excitably: "Technician to crew: Hold your hats! We're about to be passed by the _Orionad_!" "_Orionad?_ Holy Pete!" exploded Maynard. "See that this confounded screen doesn't fail. If it dies, so do we!" "Huh?" asked Kane.