Explains the back story of Harley Quinn, a psychiatrist at Arkham Asylum who became obsessed with the Joker and turned into his demented sidekick to battle against Batman and Robin.

"Harley Quinn loves fighting crime with her classmates like Wonder Woman, Batgirl, and Supergirl, but she always does it her with own madcap style--and a big mallet! It's no surprise that Harley can't resist getting involved with an upcoming inter-school battle of the bands and a fantastic cosmic carnival that appears only once a year--and this year, it's coming to Earth! But as things get stranger, Harley knows how to get to the bottom of a mystery--and...

Traces Harleen Quinzel's journey from precocious, revenge-obsessed teenage girl to a hardcore justice-seeker on her way to becoming supervillain, Harley Quinn.