As stated on Disney Wiki, “Donald leaves Huey, Dewey and Louie to stay with Uncle Scrooge McDuck, and they prove to be such a nuisance to him and his butler Duckworth that Scrooge hires Betina Beakley as their nanny. Meanwhile, the Beagle Boys break into the mansion, and Mrs. Beakley’s granddaughter Webby (incorrectly referred to as Mrs. Beakley’s niece in this book), is the only one who catches them in the act.”