The former residents of Nemo Lagoon are settling down happily at Paradise Reef after braving many dangers, including the threat posed by the blue-ringed octopus Queen Hildraga and her army of dangerous fishes. But when Hildraga's old friend pays her a visit, the octopus sees a chance at revenge-and perhaps claim Paradise Reef for herself.
Recuperating at a reef with some Cleaner Shrimps after an encounter with human fishermen, Myrtle the Turtle and his new friend, a young shark named Denise, learn of Queen Hildraga's plan to attack Paradise Reef. But with their wounds, how will they get to Paradise Reef on time and warn its residents?