Season 1, Episode 1 - "The Bat in the Belfry"
After stopping a heist by Rupert Thorne, Batman returns to the Batcave to learn that all criminals in Arkham Asylum have mysteriously been released. Batman finds out that it's a crazed clown named, "The Joker" who released them, and he plans to make a blimp full of Joker Gas to explode over Gotham so that every citizen turns into a lunatic.
