From a technical standpoint, Virginia knew that the operation of the space-resonant science required the presence of the space-resonant elements. Even though she knew nothing of Earth Three and its highly advanced techniques which permitted the operation of a view-and-voice-operated mechanism without the presence of the elements in the area of transmission, Virginia was correct in her assumption that no passage from one time-zone to the other was possible without a critical mass of the ultra-rare transuranic elements in the receptor-zone. Having used the technique for many years Virginia and the rest in Earth Two could be certain that the only critical mass of these rare elements on Earth One was in Ed Bronson's laboratory. So, the first thing was to protect herself, to isolate herself on Earth One and to seal up forever the passageway. All Virginia had to do was to break up Ed Bronson's mass into subcritical sizes--and then to keep all other discrete bits of the space-resonant elements from being collected for a period that surpassed the possible time required for the final death of the ill-fated temporal division--the end of Earth Two. Impulsively, Virginia opened her bag and handed the automatic to Bronson. "Here," she whispered, "this may help--if they're still here!" It was hours later. Bronson's re-entry into his home was careful and stealthy but unproductive, for Peter Moray had gone back to Earth Two to await developments. Virginia knew this and was prepared for the lack of population in the Bronson home. Once the place was known to be free of invaders Bronson relaxed. "Me," he said with a yawn, "I'm tired." "I don't suppose you got much sleep last night," smiled Virginia. "Darned little," he agreed. "And I'll get less until we figure out something to do with this equipment of mine. Obviously it does not require energization to permit the effect." "Why not seal the thing in a metal case of some sort?" suggested Virginia. "Think it might work?" "Maybe. At best, if you shield it well and keep it canned up, you can be certain that anybody that comes through will emerge in a dark, confined place." "Not necessarily," said Bronson. "Radio waves often disregard things like shields and closed rooms. And, if I recall correctly, that feller who came through and clipped me was parked out on the middle of the floor some ten feet from the crystal." "If you're tired," suggested Virginia, "why not take it easy? You take a snooze and I'll keep watch. You'll think better once you've had a bit of rest." "But what will you do if--" Virginia smiled. She went to Bronson and touched his hip pocket with the back of her hand. Ed nodded and took the automatic out of the hip pocket and handed it to her. "I can't cover eight shots with the ace of spades," she said, hefting the gun, "but I'd not miss an invader."