Hi! I'm new.
Anyways, here's my idea for a third movie:
In Long Halloween we had the Holiday killer and in Dark Victory there was the Hangman killer. In Long Halloween the killer was going around killing mobsters like Carmine Falcone. It turned out being two people, Harvey Dent and either his wife Gilda or Alberto Falcone, son of Carmine. The Hangman killer was Sofia Falcone Gigante, daughter of Carmine.
So, I'm saying that you can combine the idea of the Hangman and Holiday killers into one character. The last place we saw Carmine Falcone was where? Arkham. Where am I assuming Two-face is at the end of this film? Arkham. This Hangman/Holiday killer shows up to kill Falcone in Arkham, and during the commotion or whatever... Harvey Dent escapes. Leading everyone to believe Harvey killed Falcone and escaped.
This is when Selina Kyle can enter the picture. In the comic, it's pretty much shown that Selina is the illegitimate daughter of Carmine Falcone. She shows up in Gotham to start looking for some kind of proof that the man who just died is in fact her father. She's already been a cat burglar for a while, so, she breaks into Falcones house one night looking for any type of connection she can find. Batman catches her breaking in, a fight ensues. As the film goes on, it's shown she likes to hang out with the higher up in Gotham, which is how she meets Bruce.
While all this is going on mobsters start falling left and right. Gordon and Batman start collecting clues to find out who's behind the murders. Gordon wants to catch Dent, Batman wants to redeem him. Little do they know, the killer is not Dent at all, but someone else. While this is happening, Dent makes some public appearances to show what Batman and Gordon had done to him. He tries to convince Gotham they need someone willing to kill the villains to make it truly clean.
After a few more confrontations, Batman finally catches up to Harvey, who is about to murder Alberto Falcone, the son of Carmine Falcone. Alberto had broken into Arkham to kill his father so he could finally get all of his assets, but then let loose some of the inmates to set the blame on someone else, not knowing that Harvey was one of them. Alberto planned on using the money to give power back to the mobs of Gotham City, but first he had to establish a new order by killing the leaders of the old families.
Harvey had been working behind the scenes, trying to find out who was the mastermind behind this plan, and who was pumping money into these new families that were popping up in the old ones places.
Anyways, lots of stuff happens here... not sure what. It's a rough idea I just came up with.
It's a real loose interpretation, but in my mind... the perfect place to go as to tie the first and second film more tightly, and bring the story to a suitable conclusion.