Find the entrance to the laboratory

The documents from the military mention the underground laboratory X-18, which is your next target. Barkeep said that it's locked and only Hog, the bandit leader in Dark Valley, has the key.
== Walkthrough ==
Travel to the Dark Valley and talk to Hog. He will give you the key in exchange for finishing a mission called Helicopter crash.
== Notes ==
* Your first arrival into the Dark Valley might be critical for your achievements if you're a completionist. Refer to Free the Duty squad for the detailed explanation.
== Bugs ==