Once the battle is won, wait for officer Cash and Oracle to contact Batman. The information they will give you will point you back to the Panessa Studios. Similarly to previous visits to this location, use the door on the roof and the elevator.
Enter the quarantine zone and walk towards the cell in which Batman has earlier placed Robin. Listen to Scarecrow's talk and leave the place (if you want, you can talk with Harley Quinn, but it's not mandatory).