The bartender will be your next quest giver. The documents mention a secret X-18 base somewhere in the Dark Valley area. The door to the laboratory requires two keys. The bartender will give you one, and you'll have to get the other from a bandit nicknamed Borov, who has set up camp near the laboratory entrance. To the Dark Valley.
This location have a lot of sidequests. Its the heart of the game.
See also:
What to do in the Agroprom Research Institute dungeon?