Trouble aboard the satellite observatory which has been established to circle the Earth every four hours. It is under the despotic control of a brilliant but unbalanced scientist, Commander Hendricks, who refuses to allow his staff any means of communicating with Earth on their own account. But he doesn't know that Tony Hale, who is one of the engineers in the observatory, has smuggled in his homemade transistor radio.Scientists everywhere are baffled when three brown streaks appear on the Earth's surface, destroying all the vegetation in their path. No one can find the explanation until it is realised that the streaks lie in the direction of the satellite's orbit. Hendricks first refuses to reply to any questions and then announces that he intends to be the world dictator; if the governments of the world refuse to agree he will starve them into surrender by destroying all the vegetation on Earth. The situation seems desperate. But Tony has already used his transistor radio to get in touch with a friend on Earth. His homemade set is now the only means of contact between Earth and the observatory, and through it plans can be made to deal with Hendricks - plans in which Chris Godfrey has a leading role to play.