Beloved King Louis VII, ruler of Planet Caspia, has died. If anything befalls his only son, Prince Heace, the throne will default to the villainous Duke Ruber. The Queen has called in the Dirty Pair to ensure the Prince's safe return.

Sundric, a brilliant cryptanalyst and deadly assassin, has eluded the 3WA for thirteen years, but they have one last chance to catch him. The Dirty Pair go undercover as Flight Attendant Yuri and Sister Kei to smoke him out!