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This is the first part of 2 parts in the Terminus Mission in Hitman Absolution. In this part you have to gain access to the upper level of the Terminus Hotel. This guide is for completing this part on the hardest, purist, difficulty but not a guide to completing all the challenges in this area.
There is an access point at the left side of the Terminus Hotel. Go up to it and take the stairs down.
When you are down in the sewers area go into the broken pipe. At the back of it you can jump up to a ledge. When you get up to the top there is a guard patrolling in the corridor ahead. Take the wrench near the ledge you climbed up and throw it into the staircase to distract the guard.
Once the guard has walked up the staircase follow the corridor to the maintenance area where there is a worker walking about. He doesn't get suspicious of you, even in your suit. On the left wall of that area is a air ventilation shaft.
Enter the shaft and go through it. You don't have to worry about any guards on the other end. There is a disguise lying on the table ahead. Put it on. Exit this room through the door to your right.
There is a Terminus Hotel Employee up ahead, but he turns and goes. Remember, they are the only people that will get suspicious of you if they see you. Follow the employee until you get to some boxes.
Stay behind these boxes until you can see another employee walking past (you can just make him out through the little window in the image above). Then walk through the doorway to the left up to the elevator. Call the elevator and enter it. You can just stand in front of the elevator until it arrives. This is the end of the downstairs area.