Following the Clues in Highland Park

Chapter 6 - Moving Shadows Decrypted data contained in a dead man's neural hub pointed Jensen to an abandoned factory complex in Highland Park. Flown there by Faridah Malik, Jensen sets out to investigate the area. Little does he suspect what he will find...

M10 - Following the Clues in Highland Park is a mission in Deus Ex: Human Revolution.

Infilitrate the mercenary compound
Jensen finds himself in a parking lot filled with guards. The goal is to enter the nearby warehouse and take the elevator inside the warehouse down into FEMA's compound. Beyond simply fighting your way though, there are several ways to enter the warehouse. Inside the warehouse itself are four more guards on patrol, a sniper in a catwalk, and a guard in a security shack. The elevator itself is down a ramp. A vent system connects the first floor and the catwalk. Call and enter the elevator to finish this part of the mission.
 * Directly across the parking lot from the door through which you entered this area is a fenced-off section with a hackable lock. Hack the lock, enter, then take the ladder located there to a door in the roof.
 * Almost directly beneath the roof door is a door on the ground floor. There is a guard stationed immediately before this entryway
 * On the far side of the warehouses are some boxes. Jump over these to reach the back

Locate the mercenary leader
The elevator takes Jensen down through a series of floors, each of which has guards engaged in various preparations. These guards cannot see you in the elevator. However, when the elevator ends, be ready to move. You find yourself in a large room. On the ground floor is a 80-X Boxguard and two soldiers. Above them is a series of catwalks with a further three soldiers. To sneak across this room you can: Once through, you are in a passageway in which two guards are talking. Eventually one of them will leave while the other will begin a patrol. You can take him out. There is also a ladder that leads to an upper corridor that will take you right past this guard. Both ways lead to a large FEMA holding center. However, both ways also offer different options. The holding center itself has two levels. The upper level consists of a series of catwalks patrolled by three guards and monitored by one camera. You can sneak past these guards or, with careful timing, take them out. The ground floor consists of a series of holding cells, a turret, cameras, and several patrolling guards. Upon first entering the lower level, there is a vent hidden behind a box immediately to your left which makes it easy to sneak past the guards. Alternatively, using the ground floor security office to change the turret to ENEMIES makes the whole room much easier.
 * Go right. To the right is an entry to a stairwell that leads up to the catwalks. You must evade two cameras on the way up. Once there, either take out the guards or sneak past them.
 * Go left. There is a large holding area in this direction, access to which is blocked by a wall of large tubes. However, stacking the nearby crates allows you to jump over these tubes and use the cover of the holding area to move past.
 * Go up the middle. It is possible to hid beneath the platform immediately to your right upon exiting the elevator. This way is perhaps the most difficult.
 * Staying on the ground floor takes you past a security office. The security hub in this office gives you access to some of the cameras in the holding center as well as a turret.
 * The upper corridor leads to a room with a second security hub. Hacking this security hub gives you access to an armory in this room.

It is possible to explore the holding cells. There is a small amount of loot. There are also several Pocket Secretaries with messages from the people who attacked Sarif Industries. As only one guard patrols the corridors between the cells, and there are only a few cameras, it is easy to explore them without taking out everyone in the room.

Once through the holding center, you find locker rooms, a cafeteria, two medical bays, and a small armory. Depending on the route you took, you may come across two FEMA employees. The employees will not automatically attack you. If you let Zeke Sanders escape from Highland Park, then met him in Detroit as part of Voices from the Dark, you will have a password that allows you to get past these employees and a passcode to all relevant doors. If you did not have access to Sanders for whatever reason, then you can still inimidate to the employees to make them let you through, but they will attack you if you attempt to hack any doors in their presence. Whichever method you take, it is worth exploring the locker rooms, armory and medical bays for supplies. Additionally, a small room behind a level three lock contains an XP book.

Once through this area, take the elevator down to a large empty warehouse. The warehouse is initially dark. Then sirens sound and lights come on. There are no enemies here, so proceed as you like. Go to the end of the warehouse, follow the corridor behind an office, and come to a set of closed doors. Triggering these doors initiates the fight with Barrett.

Defeat Barrett
Kill Barrett by any means. Barrett's primary armament is a machine gun which can overheat. His secondary armament is throwing a cluster of grenades. If he gets in melee range, most of the time he will kill Jensen outright. Ammunition is scattered around and there is also a locker full of shotguns. A cheap way to kill him is to throw the barrels at him until he dies.

Meet Malik at the original landing site
Take the quick exit door ahead.

Barrett Tactics

 * Barrett is the first boss encounter in Human Revolution.
 * He attacks primarily with his minigun-arm, and also throws frag grenades. He will melee the player if he gets too close.
 * Barrett is vulnerable to headshots as well as EMP, concussion, gas, and frag grenades.
 * Supplies are located throughout the edges of the room and there are several pillars and boxes for cover.
 * Setting traps using UR-DED or proximity mines works well.
 * Various item in the room: boxes, fire extinguishers, gas canisters, and explosive barrels can be thrown at Barrett and many will stun him. This is a good method for sneaky players who are not outfitted with heavy weapons.
 * Barrett can be stun-locked with the stun gun and enough ammo (~25 darts on Give me a Challenge).
 * If the player hides long enough Barrett will eventually kill himself with his own grenades.
 * Best place to hide is behind the box in supply room - Barret will not enter there even if you are spotted
 * If you are hacker/sneaky type, hide-and-shoot tactic also works, however not very fast.
 * Using the rocket launcher can end this fight fast. Two hits with the rocket launcher and a few shots from the pistol or machine gun are sufficient.
 * Using the Typhoon Explosive System is effective but risky. At close range, Barrett will melee.
 * The game can be saved during the encounter.
 * A relatively easy method is to hide behind a pillar and stun him as he approaches the corner, switch to a magnum and hit him for 4-5 headshots, reload and repeat. A gas grenade or thrown gas bottle for distraction and about 5-7 headshots with the magnum also do the trick.
 * Another very easy way is to immediately sprint towards Barrett as soon as the battle starts and to shot him with the stun gun. Reload the stun gun while moving a few steps away from Barrett and then throw a fragmentation grenade at his feet. Repeating this only twice will kill Barrett on I Want a Challenge difficulty. However, be aware that the grenade explosion will take Barrett out of his stun status, so you should reload first before throwing a grenade. And alternatively, you can use UR-DEDs (one at a time) and even fragmentation mines instead of grenades.