Thief Side Mission: Eyes On The Prize

"It must be the clerk. Maybe he can help." As soon as you enter the window, Garrett gives you a big clue. Use focus, and you'll see that there's a pressure plate near the window. Pick up the clerk's dead body, and throw him on it. This opens the door to the next room.

There is a switch and an electric box inside. Use both, grab the loot, and head back toward the window. Just to your left is a door that you have to lock pick to open. Drop down the hole, and your telescope piece is inside a night stand. There is also some ammo on the shelves.