Lucky Starr and the Oceans of Venus

Lucky Starr and the Oceans of Venus is the third novel in the Lucky Starr series written by the legendary Isaac Asimov, author of I, Robot, Foundation, and the Galactic Empire series. The Lucky Starr series was originally published under the pseudonym Paul French.From a distance it seemed an emerald green, fairyland bubble!Aphrodite, the largest city on Venus, deep beneath the planet's sea. Earthmen had established an incredible civilization, but now it is threatened by an unknown force preying on men's minds."Bigman's head snapped back at a sudden new and strange sound. It was a voice, flat, without intonation. It said, "Do not tamper with your machine of far-reaching sound. We do not wish it."Bigman turned. His mouth fell open and, for a moment, stayed so. He said, "Who said that? Where is it?"Lucky said, "Easy, Bigman. It was inside your head."How will Lucky Starr fight off an enemy that can get inside people's heads?