The Warehouse Key is a silver mechanically cut key used to open a door to the warehouse portion of the docks outside of the Boston quarantine zone. It is used and protected by Robert's's henchmen to allow access to the docks.
The Warehouse Key is found during the second chapter, "The Quarantine Zone", in the section "The Slums". After Joel and Tess drop through a hole in a fence to advance to the docks, two of Robert's's men appear. This is the activation scene teaching the player how to stealth kill human enemies. After killing the two men, there are two more guys inside the nearby building. Killing one of the guys will drop the key. This is required to advance through the chapter.
- This key is 100% identical to the Pharmacy Key.