Behind the bookcase is a small room containing a safe.  Use your audio sensor to listen to the lock mechanism.   You should be able to work out the combination (reveal).  Click the handle to reset the mechanism if you make a mistake and start again.

Once inside the safe take everything except the teddy-bear (you can't take him anyway, sorry!).

Read the instruction sheet on how to use the code calculator.

Leave the safe room, leave the room with the desk.   Near where you originally entered this room there is another door with a card-reader.  Go to that door and use your code analyser to crack the code (reveal).   The code was on the palmtop computer in the office with the desk.

Once inside you will see two boxes on the wall to your right.   These have the video feeds from the security cameras.