Warning: The following contains SPOILERS for Batman: The Long Halloween Part One.
Warner Bros. Animation's latest animated Batman film for adults, One, has a post-credits scene that sets up the second half of the long-awaited adaptation. Based on one of the most popular Batman stories of all time, The Long Halloween is set early in the Dark Knight Detective's career, as a battle brews between the established mob families who have ruled Gotham City for generations and the costumed criminals that challenge the status quo of the underworld. The Long Halloween also details the downfall of Gotham City District Attorney Harvey Dent and how he became the criminal mastermind Two-Face.
Batman: The Long Halloween Part One covers the first four chapters of the original 13-part storyline, ending with the death of Alberto Falcone at a New Year's Eve party held by his father, crime-boss Carmine "The Roman" Falcone. Alberto's death marked him as the latest victim of Holiday; a mysterious murderer who seemed to be targeting Carmine Falcone's associates. The post-credits scene was set at Alberto Falcone's funeral — an event that was not depicted in the original Long Halloween graphic novel.
After the ceremony, Carmine Falcone and a female associate approached Bruce Wayne, whom Falcone had hoped to business with, as he had once done business with Bruce's father. When Bruce once again refused Falcone's invitation (knowing that he wanted to use the Wayne Foundation to launder his ill-gotten gains) Falcone apologized for his rudeness in failing to introduce his associate. Bruce took the woman's hand and a thin, thorny vine snaked from out of her sleeve. A moment later, Bruce seemed dumbstruck, as his dark eyes turned a bright shade of green. The scene ended with a close-up on Falcone's associate as she smiled, revealing her to be Poison Ivy.
Apart from Alberto Falcone's funeral being shown, this scene marks a significant change from the original Long Halloween comics. While Carmine Falcone did hire Poison Ivy to help him take control of Bruce Wayne and make him more agreeable to doing business with Falcone, their partnership was not revealed until much later in the story. Also, rather than approach Bruce Wayne at a funeral with Carmine Falcone at her side, Poison Ivy infected him with her mind-control pheromones while posing as a flower-seller. She "accidentally" pricked Bruce Wayne's finger with the thorns of one of her roses, while he was on a date with Selina Kyle.
In the original comics, this led to Catwoman taking action after she realized what Poison Ivy was up to, following a chance interaction with Bruce Wayne where he completely ignored her on the street to hurry into a car where Poison Ivy was waiting for him. Presumably the same will happen in Batman: The Long Halloween Part 2. However, it is not clear if Poison Ivy will maintain control of Bruce Wayne for the better part of a month (as she did in the comics) or if she will manipulate his mind and his business for longer than that.
