"Nothing on communication with base?"
Keller shook his head.
Burke said evenly, "I figured out three chances for us—all slim ones. The first was to find the garrison when the radio summons didn't and get it or its descendants to help. I found the garrison—on Earth. No help there. The second chance was finding the civilization that had built this fortress. It looks like it's collapsed. There's been time for a new civilization to get started, but it's run away. The third chance is the slimmest of all. It's hooking together something to fight with."
Keller reached out over the array of cubes that had been experienced by Holmes and himself while using the helmets from the cube-library. One cube had been set aside. Keller put it in place on the extra helmet and handed it to Burke.
"Try it," said Keller.
Burke put the helmet on his head.
He was in this same instrument-room, but he wore a uniform and he sat at an instrument-board. He knew that there were drone service-boats perhaps ten thousand miles out, perhaps a hundred. They'd been fitted out to make a mock attack on the fortress. Counter-tactics men devised them. There was reason for worry. Three times, now, drones pretending to be Enemy ships had dodged past the screen of globes set out to prevent just such an evasion. Once, one of the drones had gloatingly touched the stone of the fortress' outer surface. This was triumph for the counter-tactics crew, but it was proof that an Enemy ship could have wiped out the fortress and all its garrison a hundred times over.
Burke sweated. There was a speck with a yellow ring about it. It was a globe, poised and ready to dart in any conceivable direction if an Enemy detection-device ranged it. The globes did not go seeking an Enemy. They placed themselves where they would be sought. They set themselves up as targets. But when a radar-pulse touched them, they flung themselves at its source, their reflex chooser-circuits pouring incredible power into a beam of the same characteristics as the radar-touch. That beam, of course, paralyzed or burned out the Enemy device necessarily tuned to it. And the globes plunged at the thing which had found them. They accelerated at a hundred and sixty gravities and mere high explosive would be wasted if they carried it. Nothing could stand their impact. Nothing!
But in drills three drones had dodged them. The counter-tactics men understood the drones, of course, as it was hoped the Enemy did not. But it should not be possible to get to the fortress! If the fortress was vulnerable, so was the Empire. If the Empire was vulnerable, the Enemy would wreck its worlds, blast its cities, exterminate its population and only foulness would remain in the Galaxy.