Volume 5 of the Jan Darzek series. Like book 4, this one is another planet-sized mystery rather than the galaxy saving efforts of the second and third books.
This time, Jan and Effie help a planet that has received a message threatening it with destruction by persons unknown. If planet Vezpro does not comply with a series of impossible demands, the anonymous author of the threat claims he will turn turn their planet into a star. In a galactic civilization that knows no crime, the planet's government doesn't know how to react. Is it a joke? A hoax? A real threat? Jan Darzek is from Earth, a planet rife with crime and criminals, so he's the natural person to call on for help.
The first clue that turns up is a report of an uninhabited planet elsewhere in the galaxy that has mysteriously turned into a star, as if someone were practicing a technique they might want to use on Vezpro. The second clue is a radiation burned and unconscious man who appears out of nowhere on the planet Skarnaf. But how are these two events connected? Are they just coincidences? There are plenty of suspects and not enough time. And, a bit of a spoiler: there is no actual Whirligig of Time; it's just a quote from Shakespeare meant to give the reader one extra clue that Jan Darzek doesn't have - can you solve the mystery before he does?