Houghton returns from vacation to the Station, located in the endless ocean of Venus. He is pleased to meet with scientists working on the planet and with a representative of local life - the delphoid Oscar. Of all those present, only Houghton believes that the Delphoids are an intelligent, but not a man-made race. And there is direct confirmation of this. Meanwhile, geologist Dykstra completed his research and proved that through targeted nuclear explosions it is possible to turn Venus into an Earth-type planet, with land and breathable air. In this case, the Venusian underwater civilization will die. And then Houghton decides to take a desperate step...