Doctor Robotnik has Bartleby arrested for treason. At the same time, the Sonic Underground must destroy a Ruby Mine with rubies so high grade, they can power lasers powerful enough to melt through solid titanium. When Sonia learns that Bartleby was arrested and is on trial, she knows she has to help him.
A notable part of the episode is the advancement on Bartleby's character. He is seen right away that he is willing to risk roboticization to protect Sonia, telling her not to try rescuing him because she could be captured. When he learns the whole trial is a plot to lure Sonia and her brothers into such a trap, he immediately decides to take roboticization to save Sonia.
After blowing up the mine, Sonia races off to save Bartleby. Sonic and Manic follow and beat her there with Sonic's speed. They save Bartleby and the two bid farewell outside of an airport.