(6) Locating mercenaries' leader Deus Ex: HR Guide

Save the game and go ahead #1, and do not bother with the ubiquitous darkness. After using the stairs turn left, following the only possible way #2. Soon you should reach a closed door. An attempt to open it will trigger a cut-scene - you'll find out that you have to confront muscular Barret.

Reward: 1750 experience points + 750 experience points for staying undetected.