The holidays are here, but not every Siren's feeling the cheer! Sure, Harley and Ivy's friendship warms to a romance, but Catwoman and millionaire Bruce Wayne go ice cold when Bruce attempts to define the relationship -- wasn't he supposed to be a playboy? And then there's the matter of Black Canary's bachelorette party, where the Sirens and the police commissioner's daughter, Barbara Gordon, are all on the guest list. Tensions ride high... and Gotham's most elusive serial killer, Horoscope, is happy to cut right through them. Literally.