Go back to the hallway and slowly move to the next open door. There is an armored dog sitting next to it, and then there will also be a nazi soldier located in the room. Then, break down the wall in the fireplace and continue on the path. You will also be able to pick up a bombenschuss scope which will allow you to kill targets easily. Continue along the balcony area until you meet up with two nazis that are talking. You can simply pass by them quickly or you can wait for them to stop talking and silently kill them with the handgun. In the next room, there will be a nazi in the back, near the fireplace, that you can take out with a handgun. Walk along the left hallway slowly and when you reach the end, prepare for a commander that will be nearby. Continue along the path and there will be another nazi soldier up ahead, as well as the commander on the other side of the balcony. Kill them both and then this area will be cleared of all the nazis.
Continue down the path and open the vent that goes to the next area. If you want to access the Nightmare Level for Chapter 3, then jump over the railing and the bed will be located in the left side of that small room. Otherwise, continue through the area and destroy the wall to the next balcony. Prepare to fight a few mor nazis on the other balconies, as there will be several. Once they're killed, you'll want to run past the area you're supposed to go to and continue going through the balcony area. At the dead end, there will be a Gold piece in the corner of the balcony. Go back and climb up through the small window area.
Crouch and slowly move to the right part of the room. In one of the bookcases to the right, there will be another Gold piece. Then go back and go through the path under the staircase. There will be a Nazi on the other side of the staircase, so be sure to kill him without alerting him, otherwise the commanders will notice and call for backup. After he is dead, look at the bookcases to the left, and you will find another Gold piece in one of them.
Go back to the staircase and slowly go up to the next floor. There will be a nazi patrolling the area, so be careful. Look over the railings and you should be able to see one of the commanders and be able to kill him. Once they're taken out, go through the door that leads out to the balcony on the right side. Go behind the boxes and you'll find another Gold piece there. Crouch and be ready to kill a few more nazis because there are two lined up that block the passage to the next commander. Once they're dealt with, simply kill the other commander and go back into the library area.
Head to the door that leads out to the right balcony area, where you got the first gold piece. To the left of that area you will find a glass container that houses a key. Grab it. Then go to the large portrait of King Otto in the very far left side of the second floor, and interact with the statue in front of it. It will open a secret door that houses a Letter and another Gold Piece.
Continue on the path and you'll be able to find Wesley in an electrocution chair. After a cutscene and seeing Welsey die, you will talk with Rudi and when he tries to electrocute you after he says "f*ck you!", then you can interact with the pipe in your leg, electrocute Rudi, and then kill his dog. Once he's dead, you'll want to immediately go into the room behind the chair, then go into the room to the left of that. Interact with the vent above that room, and pick up the Gold piece located inside. You will also find all your weapons in those rooms, so pick them up and then use the area as a base for shooting the nazis and heavy soldiers. It will be a long fight as there are a large number of them.
Once they're all dead, you'll want to go to the second floor and open the door to the elevator room. Once you call down the elevator, the ending cutscene will start, and you will begin Chapter 4 - Escape!
