But the Earthmen were not yet free. As they crouched there, watching their unknown benefactor, they felt the fierce surge of power from the Brain again. It alone did not flee. It remained there, on its platform, in the middle of the now deserted square. And if it was angry before, it was raging now, with a crimson, crackling radiance. For it was the Brain which was the object of the rocket-plane's attack. A third, fourth, and yet a fifth time the plane came sweeping back over the square. And each time it did so, the Earthmen could feel part of the crushing thought-force which the Brain hurled upward at it. Invisible weapon against invisible weapon. Atom-blast versus the Brain's super mental-force! And the Brain fought tenaciously. Such was its power that the rocket-plane was caught in its grip once, veered crazily and was almost buffeted down until an extra burst of the rockets sent it zooming away. The watching Earthmen felt that power too, and were sent spinning, bruised and battered, against the building where they crouched. But the plane's atom-blast must have begun to find the range, because soon the Brain propelled itself toward the shelter of one of the buildings. It was angry, but it was intelligent. It recognized the danger of that atom-blast. The transparent dome encasing the Brain was of very tough material, but it would have soon crumbled under a few direct and powerful blasts. It was not until the Brain had withdrawn to safety that the tension eased, and the men dared to leap across the square again, strewn with the ghastly remains of numberless Proktols. This time they were not apprehended. The mysterious rocket-plane was speeding away toward the desert, but the destruction had been so terrible that the remaining Proktols didn't care or dare to emerge. Devries spied one of the atom-blasts that he or Ross had dropped. He snatched it up, stopped and looked back speculatively, weighing the weapon in his hand. Janus pulled at him. "Come on, you don't know when you're lucky!" "Yes, but I'd like to take at least one good blast at that Brain after the way it slapped and battered us around!" Devries stumbled along after them, unwillingly. "Have you got the _Wasp_?" Janus finally managed to ask Ross. "I didn't get here through the fourth dimension! It's out on the desert there, just about a mile from here. I had a close call when they turned that flame on the _Wasp_. I got to a space-suit just in time. Kept their ship in our visipanel long enough to see they were heading back for Neptune. Took me hours to repair the _Wasp_, and hours more to find you." Ross very prudently didn't ask about Blake or Ketrik, and Janus was glad of that. * * * * * They reached the _Wasp_, and lost little time in blasting out into space. "What about that fleet of space-ships we saw down there?" Devries asked. "Can't we go down and blast them off the map?"