Mob boss Carl Grissom orders his right hand man, Jack Napier, to raid Axis Chemicals to remove any evidence of its ties to Grissom's criminal empire. Grissom secretly sets Napier up to be arrested as punishment for Napier's affair with his mistress, Alicia. During the robbery, Napier has an encounter with Batman that results in him falling into a vat of chemicals, which transforms him into the Joker.