Fan Casting

When Bruce Wayne starts receiving letters implying that someone knows he's Batman, him and Robin start investigating, and it leads them to finding the dead body of Victor Zsasz. Meanwhile during a costume party Barbara Gordan trying to get over her dad's death decides to go as a female version of Batman but on the way to the party stumbles upon a mugger stealing from an old woman and decides to help but when things get too much for her to handle Batman and Robin show up and take her back to the batcave to heal her wounds. Eventually Barbara convinces Batman to let her work with him to bring her father's killer to justice. Batman and Robin then decide to make her Batgirl and she starts helping them with their new case. They soon find a location from which the letters are coming from and when they get there, they meet the Riddler who reveals himself to be Edward Nashton aka Jim Gordan's killer. In the season finale we see Batgirl fight Riddler while Batman and Robin work with Harvey Dent to get there and capture him. It all ends with Riddler going to Arkham and him promising Batman that he will keep his secret.