"The garrison left," explained Burke, "because it was abandoned. It was left behind to stand off the Enemy, and the civilization it belonged to moved away. It was left without supplies, without equipment, without hope. It was left behind even without training to face abandonment, because its members had been trained by black cubes and only knew how to do their own highly special jobs by rote. They were just ordinary soldiers, like the Roman detachments left behind when the legions marched south from Hadrian's Wall and sailed for Gaul. So when there was nothing left for them to do but leave their post or starve--because they couldn't follow the civilization that had abandoned them--they left. The cube in the box was a message they set up for their former rulers and fellow-citizens if they ever returned. It's not a pretty message!" Sandy swallowed. "Where'd they go? What happened to them?" "They went to Earth," said Burke tonelessly. "By twos and fives and dozens, in the service ships that came out with meat, and took back passengers. The service ships had been assigned to bring out what meat the hunting-parties could kill. They took back men who were fighters and ready to face mammoths or sabre tooth tigers or anything else. Just the same, they left a transmitter to call them back if the Enemy ever came again. But it didn't come in their lifetimes, and their descendants forgot. But the transmitter remembered. It called to them. And--we were the ones to answer!" Sandy hesitated a moment. "But if the garrison went to Earth," she said dubiously, "what became of them? There aren't any traces--" "We're traces," said Burke. "They were our ancestors of ten or twenty thousand years ago. They couldn't build a civilization. They were fighting men! Could the Romans left behind at Hadrian's Wall keep up the culture of Rome? Of course not! The garrison went to Earth and turned savage, and their children's children's children built up a new civilization. And for here and for now, we're it. We've got to face the Enemy and drive him back." He stopped, and said in a tone that was almost completely steady and held no hint of despair, "It's going to be quite a job. But it's an emergency. We've got to manage it somehow." There was also an emergency on Earth, not simplified as in space by having somebody like Burke accept the burden of meeting it. The emergency stemmed from the fact that despite the best efforts of the air arm of the United States, Burke and the others had gotten out to space. They'd reached the asteroid M-387. Naturally. The United States thereupon took credit for this most creditable achievement. Inevitably. And it was instantly and frantically denounced for suspected space-imperialism, space-monopoly, and intended space-exploitation.