Start your engines! "The Clown Princess of Crime." "The Maiden of Mischief." "PhD." Call Harley Quinn anything you want, but don't you dare try to take away her cuddly-wuddly new best friend from another universe! Clear the crosswalks and fasten your seatbelts as Harls leads the Justice League and a skyful of multiversal champions through the streets of Gotham City on a physics-bending, law-breaking, rubber-burning race to the finish... that will leave one champion's life hanging in the balance!