Instructions
Exit the library. The game will label this wing of Arkham Mansion "Wayne Manor."
Continue along the corridor. The area's content will become increasingly surreal and will lead to another sequence involving Scarecrow.
Play through the Scarecrow sequence. As with the previous one, you must avoid Scarecrow's gaze and make your way to the Bat Signal. When you wake from the sequence, you will be in the mansion's bell tower.
Aim a Batarang at the bell's rope. The bell will crash through the floor.
Glide down through the hole that the bell made, returning to the mansion's ground floor. The door to the East Corridor will now be open.
Walk through the East Corridor, subduing a few enemies along the way. You will arrive at the Warden's Office. Dr. Young is inside it.