Find Strelok's flash

The  task is a storyline mission featured in S.T.A.L.K.E.R.: Lost Alpha.

"Okay, you need to find a spiral staircase, go down, then past some columns and through a machinery room. Then you'll reach some creepy hallways and smaller rooms linking them. Somewhere in there I stumbled upon a room ... like a safehouse of some sort. That's where I found some sort of book with an encrypted message, which probably leads to a flashdrive with info. The book was useless for me so I decided to leave it there cause nobody in their right mind would try to look for it in this place. On my way back I ran into a bunch of zombies - they were really worked up about something so I got out of their way and never thought of returning there. I figured the corridors would lead to another manhole and headed that way. I could already smell the fresh air when I heard a military patrol approaching. Caught between them and those damn zombies, I kept moving from room to room, hoping to stay hidden. Not sure if I'd make it. I don't know how but I finally made it out in one piece. Far as I know, the flash drive is in the underground too - but which room... I really can't be sure. Just pay close attention to the notes in the book written by Strelok."

- Detailed task information

Overview

 * This is a three part mission given to the player at the conclusion of the Save Mole mission.
 * The map given above is obtained later in the game from Ratcatcher.
 * The map relates to the Base Game where Strelok's Hideout was found up a ventilator shaft.
 * The player needs to find the Novel "Deep Darkness", Strelok's flash drive and leave the underground.
 * Map markers are placed sequentially to assist the player's investigations.
 * The mission takes place in the Agroprom Underground which should be consulted for an overview of its inhabitants and other hazards.
 * (NB: for various v1.4000 releases, the player will now need to find a "key" to gain access to Strelok's Hideout in order to complete this segment. This 'find the key' subtask is erroneously spawned as a subtask twice for the mission (v1.4005) but needs to be satisfied only once)