The Diving Probe detected a carbon biosignature in the ocean below the icy surface of Saturn's moon, Enceladus. Research ship Sagan departs with a submersible, hoping to find life there. The scientists encounter a new species. Custo demands they do not interfere with the Waterians. Tensions between the scientists and Custo escalate to critical mass. Santu protects the scientists. Santu asks the scientists to teach the sea life how to transition to land. Centra terraforms Enceladus. General Stanton sends starship Blazer to attack Custo on Enceladus. Centra chooses to exercise The Zero Option.