 Rygel and Aeryn return from a planet to Moya accompanied by another Nebari who aims to take Chiana back. The crew is temporarily mind-cleansed except the Pilot but they put a collar on him and thus take over Moya to attain the nearest Nebari territorial post. Chiana learns that her brother is alive. Crichton who is not affected by mind-cleansing thanks to Scorpius  chip, makes Chiana reveal the reason she is being chased: she knows of her people s plot to infect the galaxy with a deadly contagion. Crichton must work together with Pilot and Rygel, quickly recovered due to his fast metabolism, against the rest of the crew to rid Moya of the Nebari intruder. And they also have a spy to thank for unexpected help.