Earth's invasion by the members of a planet in another solar system similar to ours has its familiar thrills as it runs its course in the year 1977. The planet is Poppen and, basing his story on the possibilities of the young science of radaroscopy as it is being developed in Britain, the author manages an interesting mixture of fact and fiction as he writes of Professor Elrick's discovery of Nero- Poppea's dark star ""sun""- nearer to Earth than other stars. By the same radar waves that detected Nero's system, Elrick foretells the coming of the Poppean space fleet and he and his assistants and the world have a tough time defending themselves. Well versed in Earth's ways, the Poppeans have come because their own atmosphere is going liquid and their determination to stay makes their defeat more difficult. The final victory teaches a divided Earth a lesson in unity. Interesting speculations.