Hi Merrick! Julia and I will tell anyone who'll listen that this is the single most difficult part of the entire game. Timing is everything. You must RUN and jump from the bookcase that you are on, pull up onto the ledge, walk behind the guard and kill him with 2 blows before he shoots you once. Very hard. The guard needs to have turned to walk back to the left and taken 2 steps before you can start your sequence. If you give up we have saved games for just after this spot. Good luck, Nancy