When Ren (George Newbern), a young son of a lighthouse keeper, rescues a stranger foundering in the rocks near his home, he learns the man was an aide to his true father, a great King. Ren is given a magic compass crystal that guides him to a dragon who shows him that the only way to claim his heritage is to find the Thirteen Treasures of Rule. Unfortunately, a pirate ship captained by the evil Bloth (Brock Peters) is also aware of this treasure and is relentlessly pursuing Ren for it. On his side, Ren soon acquires companions like Ioz the Pirate (Hector Elizondo and Jim Cummings), Tula the Eco-Mage (Jodi Benson), and Niddler the Monkey-Bird (Frank Welker and Roddy McDowall), who help him in his quest. That quest becomes all the more urgent when Ren learns that the Dark Water, a carnivorous form of water that consumes anything it snares, threatens to envelope and destroy his world and only the treasures he seeks can stop it.