Prologue: That Thin Line Between

After events of the Batman the Animated Series episode Harley's Holiday, Harley decides to become a hero not thinking ahead of repercussions. After Arkham's odd power failure, Scarecrow works secretly on a plan that will make him more monster than man, though running into Harley's new alter ego confuses things. As Harley continues to run into old friends and enemies, the possibility of meeting with the Joker looms ever closer.