On this page of our game guide to Batman: Arkham Knight we provide a description in which we explain how to check Scarecrow's activity in Panessa Studios. You need to return to the Panessa Movie Studios and enter the quarantine zone.
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).