so TL;DR: Joker will be breaking harley out of prison/arkham/whatever at the end of the movie.

the trailers have featured TWO types of prison scenes starring harley one, pre-squad where he hair is hella faded and she looks miserable and dull; the other prison looks to be post-squad and majority of film. i mean she got tea, a book an hair dye and a new inmate uniform, all things she DOESN’T have in the proto-squad prison scene.

harley is super chill and relaxed in that type b prison from the clips. like of course it could be that she did a good job and amanda has delivered on the promise of a reduced sentence, plus goodies (hairdye, tea, book, slippies, a fuckin bed). BUUUUT from rumors about the nature of joker and harley’s relationship in the movie along with other theories i have AND the book genre of book she’s reading in that scene (a romance novel), i have this suspicion that harley is expecting a certain clown asshole to bust her ass out of there. because they make up during the amidst the squad mission because that’s how they can only are and they have their drastic ups and downs, and they are on an up swing by the end of the movie.

and of course joker will probably break her out and that will be the cliff hanger of the movie