Batman el Largo Halloween Series by Jeph Loeb, Tim Sale

Catwoman, The Joker, Poison Ivy, and The Riddler—any one of these Batman rogues may prove to be the mysterious serial killer known as “Holiday,” a murderer who kills according to the calendar. And now, a still-learning Batman must uncover the killer’s identity before they kill again!

Following the horrors of Halloween, Thanksgiving proves to be no haven for the guilty as another group of criminals falls prey to the mysterious serial killer nicknamed “Holiday.” Hot on the trail of an assassin targeting D.A. Harvey Dent, Batman finds his blocked by Solomon Grundy!

The mob and a madman calling himself Calendar Man take center stage this issue as Christmas nears, meaning “Holiday” will strike at any moment! But what part does The Joker play in the mayhem? Could he be more connected to Holiday than Batman originally believed?