Magica DeSpell is after Scrooge's lucky dime, so that she can melt it down and merge it with her amulet, which will grant her enough power to take over the world. To help her in stealing the dime, Magica helps the Beagle Boys escape from jail.
The next morning at McDuck Manor, Scrooge awaits the arrival of Webra Walters, a reporter from Duckweek Magazine, while Huey, Dewey and Louie go to the movies to see Invasion of the Quacker Snatchers. While the nephews are gone, Magica and the Beagle Boys show up outside the house. Magica then turns Burger, Big Time and Babyface into exact doubles of Huey, Dewey and Louie, respectively, but with one catch - mirrors will reflect their true forms.
The disguised Beagle Boys infiltrate the mansion. Big Time and Babyface split up from Burger while they search for the dime. Mrs. Beakley, however, forces them to dress up for when Webra Walters arrives, but she sees their true reflections in a mirror and passes out. They then meet up with Burger, who's having a tea party with Webby, and ruin her Quacky Patch doll before continuing their search for the dime.
When Miss Walters arrives, Scrooge is anxious to give her a proper interview, but Mrs. Beakley and Webby embarrass him due to their reactions to the Beagle Boys' antics. Then, when the Beagle Boys blow up the ceiling of Scrooge's study, Scrooge sends them to the nephews' room, with Duckworth guarding the door. Magica learns of this and turns herself into a double of Mrs. Beakley in order to get the Beagle Boys out.
At this point, the real Huey, Dewey and Louie come back from the movie, which had a plot involving aliens taking over peoples' bodies. This confuses things even further with two sets of nephews and two Mrs. Beakleys running around. Scrooge sends the nephews back to their room, much to their confusion, and orders "Mrs. Beakley" (Magica) to make them lunch. Magica's bizarre cooking frightens the nephews into thinking that Mrs. Beakley's body has been taken over by aliens.
Dewey and Louie split up from Huey and find the disguised Burger, who isn't behaving like Huey at all. Magica runs into Mrs. Beakley and magically renders her unconscious. Meanwhile, Huey runs into the disguised Big Time and Babyface, and unintentionally leads them to the dime. Magica finds them, turns herself back to normal, and plans to go back to her lair, bringing the real Mrs. Beakley with them. On the way back to the lair, Magica undoes the spell she cast on the Beagle Boys earlier, which affects Burger, even though he's still at the mansion. Upon being returned to his normal form, Burger confesses what's really going on to Scrooge, so Scrooge takes him, Dewey and Louie in his helicopter to Magica’s lair, while Webra "tags along".
At Magica's lair, as Magica prepares to melt down the dime, while Huey and Mrs. Beakley are tied up off to the side. Huey uses his knot untying skills to get out of the rope and steals a potion, which he uses to get Magica and the Beagle Boys’ attention. Soon Huey, Mrs. Beakley, Magica and the Beagle Boys get into a potion fight involving many transformations. In the end, Magica turns everyone back to normal and holds Huey hostage as Scrooge and the others arrive. Scrooge explains that the dime that Magica has isn't the actual Number One Dime, and that he'll offer her the real dime if she lets Huey go. She agrees, but Huey knocks both dimes out of Scrooge and Magica’s hands, mixing them up. Thinking that she has the real dime now, Magica and the Beagle Boys prepare to take over the world.
On the way home from Magica’s lair, Scrooge explains the mix-up to Miss Walters. He then explains that he pulled the old switcheroo on Magica, and wound up with the real lucky dime, while Magica has a normal one. An explosion then occurs from Magica's lair, as she attempted to melt the normal dime. Magica, furious at being fooled, swears that she will have her revenge.
- When Magica zaps Mrs. Beakley unconscious, she shouts "Bibbidi-Bobbidi-Boo!", in reference to the song from Cinderella.
Big Time: Thanks for sneakin' us out of jail, Magica. We was gettin' awfully bored waitin' for our time to run out.
Magica: How long was your sentence?
Big Time (as Dewey): Hey Babyface, get this crazed dame offa me!
Mrs. Beakley: (gasps) That's the last movie you go to! The language you come back with!
Webra Walters: Excuse me, Mrs. Beakwey, my weaders deserve a weal scoop. What's Scwooge weawwy wike?
Magica (as Mrs. Beakley): He is fool.