I am vengeance. I am the night. I am Batman!
Batman has protected Gotham for almost a decade. Gotham's criminals have all been locked up and have stayed that way for a year. Batman wasn't needed anymore, they won.
But the night has been turned against him.
Now Batman must hunt down this madman, calling themselves "Nightmare Moon" and bring them to justice.
Not to mention at 12 in the afternoon...