Anti-aircraft guns were fired. Shell-bursts came close, but not close enough. Not less than twenty enormous rockets leaped out of the water and shot up toward the sky. Some observers claimed there were more than thirty. Down to southward, where the bathyscaphe had been crushed, the planes that were dropping mines reported that four other objects broke loose from the ocean and fled for empty space at speeds too great to be estimated. Terry looked suddenly astonished. "But ... of course!" he told Deirdre. "When you need high pressure, of course you've got a weakness. You can't take concussions! Anything underwater is completely vulnerable to bombs! Whatever was down there has found out that the natives--we aborigines--have a weapon they can't face. Primitive stuff. Explosives! Chemical explosives! And creatures that can travel between planets and undoubtedly have atomic power and--who knows what else--can't fight back if we drop submarine mines on them!" A last object broke surface and hurtled skyward. Behind it, deep, deep down, there was a titanic explosion. "Ah!" said Terry. "That was a time-bomb! They've gone home for good!" * * * * * A task force of a private yacht, a fishing boat, a satellite-tracking station, an airplane carrier and a mine layer had driven off an invasion of earth. But the public could not be told that the earth had been invaded. The people who had been involved in this secret adventure had to be satisfied with the realization that they had saved mankind. After a jubilant dinner Terry and Deirdre sat in the veranda. Davis came out. He blinked at the night. "Deirdre? Terry?" "Here," said Terry. Davis joined them. They had drawn apart a little. "Good news by short-wave," said Davis. "Those rockets were picked up by radar. They divided into two groups. One headed sunward. The other headed for deep space. My guess is Venus for one group and Jupiter for the other. They couldn't have come from Mars. But they've gone home. Both groups." Terry paused, and then said wryly, "Two races! Some of the bolides were bullet-shaped and some were globular. That figures. But two races capable of space travel and both in our own solar system!" Davis grimaced. "We've been talking about it. Our guess is that the Venus race developed in deep water, and therefore at high pressure. And anything that developed on the solid surface of Jupiter would also be accustomed to extremely high pressure."