Batman teams up with John Constantine, Zatanna, and Swamp Thing when Solomon Grundy tries to raise a zombie army

Cain the Caretaker tells the audience a Halloween story about the House of Mystery, where Batman, Zatanna, Constantine, and Doctor Fate are turned into 10-year-olds by Klarion the Witch Boy. Now, the 10-year-old Justice League must find a way to defeat Klarion, turn them back to normal, and escape the House of Mystery before it disappears by midnight.

After defeating Harley Quinn, Batman and Zatanna encounter Brother Night who used his dark magic to control the Batmobile and kidnapping Zatanna. With the help of Etrigan the Demon, Batman must save her, stop the Batmobile, and defeat Brother Night.

Felix Faust steals Zatanna's hat in order to free a massive demon and get his youth back. While Batman and Etrigan face off against the demon, Zatanna uses every trick in her arsenal to get her hat back from Felix Faust.

Green Arrow and Plastic Man just caught Solomon Grundy, who ends up with them at the the annual Justice League Christmas party, what can go wrong? It all works out with help of Batman, the Flash and the spirit of Christmas. Although Green Arrow tries his best, the rest of the League decides to go to the S.T.A.R. labs Christmas party after all.