The Whirligig of Time — Lloyd Biggle Jr.

Jan Darzek, former private detective from Earth and now First Councilor of the Galaxy, has encountered his most baffling case. The planet Nifron D has been inexplicably turned into a sun. A quarter of a galaxy away, a native on the planet Skarnaf has been found horribly disfigured by an impossibly massive dose of radiation. While Darzek searches for a connection between the two events, the populous and prosperous world of Vezpro receives a blackmail letter that threatens it with the fate of Nifron D. In a crimeless society, has a master scientist turned master criminal? Darzek must decide quickly whether the letter is a monstrous hoax. If it is not, how can the impossible demands be met -- or five billion inhabitants evacuated in time?