Keller said mildly, "What did he do?"
Burke considered.
"The drone, faking to be an enemy, had dumped something out into space. Metal powder, perhaps. It made a cloud in emptiness. Then the drone drew off and threw a radar-beam on the cloud of metal particles. The beam bounced in all directions. When a globe picked it up, it shot for the phony metal-powder target. It went right through and off into space. Other globes fell for the same trick. When they were all gone, the drones could have come right up to the fort."
He was almost interested. He'd felt, at least, the sweating earnestness of an unknown member of this garrison, dead some thousands of years, as he tried to make a good showing in a battle drill.
"So he changed the reflex circuits," Burke added. "He stopped his globes from homing on radar frequencies. He made them home on frequencies that wouldn't bounce." Then he said in surprise, "But they didn't hit, at that! The drones blew up before the globes got to them! They were exploding from the burning-out of all their equipment before the globes got there!"
Keller nodded. He said sorrowfully, "So clever, our ancestors. But not clever enough!"
"Of our chances," said Burke, "or what I think are chances, the least promising seems to be the idea of trying to hook something together to fight with." He considered, and then smiled very faintly. "You saw movements you couldn't identify in the vision-plates? Sandy says she saw something alive. I wonder if something besides us answered the space-call and got into the fortress by a different way, and has been hiding out, afraid of us."
Keller shook his head.
"I don't believe it either," admitted Burke. "It seems crazy. But it might be true. It might. I'm scraping the bottom of the barrel for solutions to our problem."
Keller shook his head again. Burke shrugged and went out of the instrument-room. He went down the stairs and the first long corridor, and past the long rows of emplacements in which were set the hunkering metal monsters he'd cube-dreamed of using, but which would be of no conceivable use against speeding, whirling, artificial-gravity fields with the pull and the mass of suns.