Louie accidentally spends Scrooge’s Number One Dime and turns to mad inventor Gyro Gearloose for help to get it back, while Dewey and Webby become entangled in a conspiracy.
At McDuck Manor, Scrooge finds Louie sitting around watching TV and lazily refusing to do anything, and even throwing away a perfectly good phone rather than charging it because "We're rich!" to which Scrooge retorts "No, I'M RICH!" He thus decides to take Louie to the Money Bin to teach him the value of a hard day's work. Meanwhile, Dewey sneaks into Webby's room and goes looking through one of her books, only to be caught by Webby. Confronted, he admits that he's looking for information on his mother Della Duck, as he has only a photograph her and his Uncle Donald's statements that "She's gone." Webby proves to be similarly bereft of information, as Scrooge appears to have actively eliminated all photographic and printed evidence of her existence.
Thinking of one possible source to which they may look, Webby drags Dewey along as they accompany Scrooge and Louie to the Money Bin, with Launchpad driving them. The two then excuse themselves and go to visit Scrooge's archives, where they are greeted by Mrs. Quackfaster. Scrooge takes Louie upstairs and shows him a display he claims to be his Number One Dime. He then takes Louie to the boardroom where the board of directors-led by Bentley Buzzard-have once again come to Scrooge insisting that he cut spending in some area.
While Dewey and Webby are given a set of "trials" to pass by Quackmaster-which suspiciously resemble ordinary library work-the board meeting is broken into by Gyro Gearloose, Scrooge's top inventor. Gyro presents his latest invention, Little Bulb, which he claims will eliminate the need for anyone to do their own work. Louie is immediately enthralled, but the socially inept Gyro is quickly dismissed by the board, with Scrooge likewise disdaining the idea due to his own work ethic. Louie, feeling board, tries to get a soda from a machine and finding himself a dime short, steals the dime from the display case. However, upon reentering the boardroom he hears Scrooge telling the story of how he earned his first dime and it's role in inspiring his move to America and subsequent fortune.
Desperate to recover the dime, Louie convinces Gyro that he's Scrooge's rich nephew so he can borrow Little Bulb to get into the money sorting room, and then puts the aggressive robot to work looking for the dime. Meanwhile, in the archives, Dewey becomes fed up with Quackmaster's trials and attempts to leave, only to be attacked by Quackmaster herself wielding a sword. Little Bulb, having converted the money sorting machine into a massive robot body for itself, begins obsessively attempting to collect any and all dimes, and Louie is forced to flee from it with the display dime. Gyro attempts to intervene as well, and inadvertently gives Scrooge a means of convincing the board of directors that they can't fire anyone from the money bin, as they would seek revenge.
Louie and the dime end up in the bin, and Gyro is eventually able to trace Little Bulb's issues to an incorrect wattage and shuts down his giant robot form. Dewey and Webby, meanwhile, finally uncover a book mentioning Della after Quackmaster points it out to them, and after reorganizing a section of the library discover a secret room containing material about her. Upon finding a note that seems to indicate that Della betrayed Scrooge by stealing the Spear of Selene, Dewey decides that they need to find out more before he tells his brothers.
Louie successfully returns the dime to the display case, only to have Scrooge give it to him, revealing that the real Number One Dime is actually part of a pendant he wears around his neck. Louie inadvertently spends the dime, while Gyro begins contemplating Project Blatherskite.