When Arnold proposes building a skateboard ramp, she gets her father, Big Bob, to team up with Nick Vermicelli and Scheck to agree to build one at the school, then claims that Arnold knew about this plan and just took credit for it. But eventually even Phoebe turns on her for her dirty politics, and at the last debate she apologizes and admits that Arnold didn't steal the idea.
Curly wins, though, by bribing the class (Did you know that his father owns an ice cream store? Now you do!), but Arnold thanks Helga for coming clean, and they have a really nice little conversation together.
This book is notable mostly for the bit where Arnold talks to Wolfgang about the skateboard ramp, and Wolfgang laughs and says that Helga just does such dirty tricks to mess with Arnold, because she hates him. Oh, Wolfgang. So perceptive and yet not quite perceptive enough!