Scorpius (Zodiac Series) by John Wegener

The sting is in the tail! Alex Warner rushes to Caerus to find the murderer of a Cetusian Ambassador. Between an uncooperative son of the deceased, a grumpy partner, and an enigmatic Cetusian woman, Alex has his hands full just staying sane while he investigates the crime. An Ambassador is a dangerous occupation as more are murdered in quick succession. As he frantically searches for the serial killer, Alex realises someone else is pulling the strings, someone with a much deadlier game of punishment and payback. He quickly finds himself embroiled in a conspiracy that could destroy the Galactic Confederation, subjugating one of its member races to repression and slavery. Can Alex prevent the catastrophe before it enters its final phase?