This happened in the Comic Book! Bruce Wayne temporarily retired as the Batman and Azreal, who you meet in Arkham City briefly, stepped in as the new Batman. His methods turned out to be too aggressive and violent, and so Batman took him down and returned to the cowl
After the fight with Clayface, which leaves Clayface mortally wounded, Batman takes a sip of the cure and leaves the cure in his left hand. When the generator falls, we see Clayface slip into the Lazarus pit, which indicates that he is now alive and more powerful. When we see Batman again, the cu...
This happened in the Comic Book! Bruce Wayne temporarily retired as the Batman and Azreal, who you meet in Arkham City briefly, stepped in as the new Batman. His methods turned out to be too aggressive and violent, and so Batman took him down and returned to the cowl