4 stars. Yay, another robots in space story! Unit Four is activated during a crisis-the mining station in orbit around Jupiter is under attack by aliens. YIKES! She/her/it is very quickly put through the activation protocol leaving it with strange files and a suspicious lack of information about the aliens in its data banks. The truth about the alien attackers will upend everything it has ever known and reveal a secret that will change it forever. This was a very good story with world and character building that blew my mind. Highly recommended, especially for fans of the Murderbot series.