Batman: Gotham Knights

You exit Arkham Asylum and climb the side of the tower towards the window of Jeremiah Arkham's office. You quietly open it and sneak up behind the Joker and Harley Quinn, who are waiting on you to open the door from the hallway. You use a Batarang to disarm the trap holding Jeremiah Arkham at gunpoint, and this tips the Joker and Harley off to your location in the room.

"Hello, Bellfry-Boy!" the Joker laughs, "I guess this is the part where you beat me an' my number-one gal pal up and take us downstairs to one of those awful, horrible, TERRIBLE cells?"

"Right as ever, Joker." you grumble.

"Well, it's not going to happen."

The Joker pulls out a pistol and points it at you. Meanwhile, Harley Quinn readies her gigantic mallet. You have to villains attacking you... what do you do?