Robert Culp guest stars as Arthur Farnel, an ex-con who runs a school leading and teaching their students how to break the law. Mark decides to go undercover in order to gather enough evidence to put him away.

Mark and Hardcastle take a group of misfit kids to a local prison in order to scare them straight; but while they are there, they are taken hostages by prisoners who are frustrated because of the repeated abuse from the guards and the warden.

While driving through Arizona on his way home from Las Vegas, Mark is surprised to hear the voice of Nick Damion, a rock deejay he idolized in his youth, on local radio station KKSB. Back in California, Hardcastle is working on a dedication for the Pioneers of Music Hall of Fame Museum. Hearing that the Museum needs a master of ceremonies, Mark suggests Nick Damion. Returning to Arizona, Hardcastle and McCormick try to learn something from Jeannine Alexander, KKSB's manager. After helping Damion, who has been using the alias of Joe Cross, out of a fake drug charge, Mark convinces the deejay to return with him to California. Trying to find out why someone tried to frame Damion (as well as why the deejay originally went into hiding), Hardcastle begins to investigate Kello Records, a company that had received a great deal of air time in the deejay's old radio show. At the same time, Damion, who had gone into hiding after discovering that music executive Joe Kello had killed a singer named Danny Phillips to cover up a payola scheme, realizes that he needs to go public with the story. Hardcastle's investigation proves partially unnecessary for the case is resolved when Damion publicly accuses Kello at the Museum dedication. Afterwards, Damion is shocked to discover that Hardcastle has uncovered proof that Jeannine is working with Kello. As the series' penultimate episode ends, Damion gets a new deejay job at a Los Angeles station.