The family joins a zen mermaid society to find a missing mystery, but Louie is convinced the seemingly innocent mermaids have a villainous agenda of their own.
After not speaking to each other for ten years, Donald Duck reunites with his estranged uncle Scrooge McDuck when he asks him to babysit his three triplet nephews Huey, Dewey, and Louie for the day. The boys rekindle Scrooge's sense of adventure, and he invites Donald and the boys to live at McDuck Manor with him, along with his housekeeper Mrs. Beakley and her granddaughter Webby Vanderquack. Together, along with Scrooge's chauffeur and pilot Launchpad McQuack, the Ducks go on many new treasure-hunting expeditions and globe-trotting adventures while contending with villains like Flintheart Glomgold, the Beagle Boys, and Mark Beaks.