In flashback, a young Bruce Wayne is watching an episode of his favorite show, The Gray Ghost. Cutting between the past and the present, the same thing is seen happening in the present as in the TV show: a whirring sound is heard, followed by a massive explosion that destroys a building. The police receive a ransom note, signed "The Mad Bomber." In the show, the Gray Ghost is shown jumping off a neighboring building to investigate, while in the present Batman does the exact same thing.
Batman sees the connection, but does not remember the end of the episode, since he fell asleep before it was over. Bruce Wayne tries to find a tape of the show, but is told that it is impossible to find, as the prints were lost in a studio fire. Looking up the show at the library, Bruce finds Simon Trent, the actor who played the Gray Ghost is still alive, and is living in Gotham.
An elderly Trent is shown living in a seedy apartment, with his landlord demanding the unpaid rent. Trent gets a call from his agent, and finds he has been rejected for another part. He has been unable to get work since his glory days as the Gray Ghost, due to being typecast. In despair, Trent trashes his apartment in a rage. Fed up with his Gray Ghost memorabilia, he takes it all to a toy store, selling it for as much as the owner, a young man named Ted, is willing to pay.
Trent returns home and falls asleep. When he wakes up all his stuff has been returned, and a note from Batman is attached to his Gray Ghost costume, summoning Trent to a meeting.
Trent shows up and Batman asks for his help. Trent says he doesn't remember the details of the "Mad Bomber" episode; he made hundreds of them. He angrily tells Batman to leave him alone, but then the same whirring noise is heard, and the Gotham Bank explodes. Batman goes to investigate, while Trent runs back to his home.
When Trent arrives, Batman is already there. Trent reluctantly opens his closet and reveals old film reels: a complete collection of "The Gray Ghost." He gives Batman the episode, and asks to be left in peace. Bruce watches the film at home (enjoying it), and discovers the source of the whirring noise: radio-controlled toy cars, carrying explosives. Forewarned, he and the police lie in wait at the next target, the Gotham Library. As a set of cars speed toward the library, one is destroyed by a police sniper, another by Batman with a flamethrower. The last car breaks off and Batman pursues it into an alley. At the end of the alley, he finds the car is a decoy, and turns to see another trio of cars racing toward him.
Batman is trapped, but then a rope falls from above, and Batman climbs it just as the cars hit and explode. Reaching the top, Batman finds Trent, dressed in full costume. Batman gives him the toy car, which Trent identifies as an authentic piece of Gray Ghost merchandise. Batman invites the Gray Ghost to help him. Trent hesitates, but then another set of toy cars appear. Both heroes jump into the Batmobile and speed away, managing to evade and detonate the cars harmlessly.
Batman takes the Gray Ghost to the Batcave. The Gray Ghost notices its similarity to the "Gray Ghost Lair" from the TV show. Batman also reveals a special corner where he still keeps some Gray Ghost merchandise from his childhood. He tells Trent he watched him as a child, and that the Gray Ghost was an inspiration to him. Trent says, "So it wasn't all for nothing..."
Batman scans the car for fingerprints, and finds Trent's on it. He turns and confronts him. Trent swears he's innocent, he sold his toy cars a long time ago... meaning the Mad Bomber is Ted, the toy collector. Batman confronts Ted, who is obsessed with toys, and needs the money to buy more. He traps Batman with a ring of toy cars, but then Trent appears in costume and takes him down. A fire starts, and they escape the building before an explosion destroys the toy shop. Ted cries for the loss of his toys and is taken into police custody.
Trent is hailed as a hero, and his career is re-started by the release of "The Gray Ghost" on DVD and broadcast television. He has been offered a part in a film, and his merchandise is now highly valuable. While signing autographs at a convention, he is approached by Bruce Wayne, who says that he used to watch "The Gray Ghost" with his father, and the Gray Ghost was his hero. Having heard these same words from Batman, Trent probably suspects who Bruce Wayne really is, which he acknowledges with a smile.