Harleen Quinzel battles her Harley Quinn alter ego while searching for the missing Joker. A new villain emerges to control Gotham's underworld in the Joker's absence.

With Batman and The Joker mysteriously missing from Gotham, Harleen Quinzel struggles to keep her alternate personality Harley Quinn suppressed as she is determined to find her "Mistah J". Meanwhile a new villain looks to take over the Gotham streets in The Jokers absence.