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
Enter the compound. Jensen can do this by entering the warehouse by:
 * Hacking a computer and entering via a roof door.
 * Enter through the ground floor door
 * Jump over some boxes at the back
 * In the yard is a fence which provides an easy access to the building
 * In the building near the elevator is an ammo capacity upgrade

Once inside the warehouse take the elevator at the bottom of the ramp to complete this objective.

Locate the mercenary leader
Just before the operating theater is a camera and a computer room, in this room is a reload speed mod behind a box. At the end of the detention blocks is 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 untill he dies

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

Notes:
One of the options for getting to the elevator is to bluff your way past two guards. When bluffing Adam Jensen tells them the 'code' to get through the door, which turns out to be the real code. However, it won't be stored in your data so you have to remember what it is (7984).

Tactical suggestions to defeat Barrett
Barrett is the first boss encounter in Human Revolution. He attacks primarily with his minigun-arm, and also throws frag grenades. On higher difficulties, one frag grenade can kill Jensen and must be avoided. Though a boss and thus much tougher than any ordinary enemy, headshots still do much more damage to Barrett, so the player should aim for his head whenever possible.

Barrett is fought in a room with several pillars and boxes for cover. There are supplies located all throughout the room, including valuable grenades. The pillars must be used to take cover from Barrett's minigun fire, but Jensen must move from pillar to pillar to avoid Barrett's grenades. Barrett will also walk towards Jensen whenever firing, and the player should keep a healthy distance between Jensen and Barrett.

If UR-DED is available at the start of the fight hide behind the pillar on the to your right deploy some UR-DED's, 4 worked fine on normal, when he rounds the corner to kill you run away and detonate, job done.

Barrett, being an augmented human, is stunned by all three types of nonlethal grenades - concussion, gas, and EMP. Concussive grenades, being the least valuable, are best, but without the flash suppression augmentation Jensen will also be blinded by the flash, so the player should take care to use cover; EMP grenades seem to incapacitate him for a few moments longer. With enough grenades and perfect timing, it is possible to kill Barrett without him ever being able to defend himself.

If the player does not have any grenades, it is also possible to pick up the various gas canisters in the room and throw them at Barrett. They will explode on impact and also stun him. This also works with the explosive barrels - frag grenades and explosive barrels do quite a bit of damage to Barrett and it's possible to kill him very quickly with either.

It's also possible, though somewhat tedious, to win this fight with the stun gun by repeatedly zapping Barrett. Shocking him with the stun gun stuns him temporarily and prevents him from both shooting or throwing his grenades, so the player can run circles around him while zapping him repeatedly. If you rush in and zap quickly enough, Barrett won't even get the chance to shoot at you. After Barrett is defeated, the player should collect all the supplies left over in the room.

It is possible to hide from Barrett if the player can get to cover quickly and leave Barrett's line of sight. If available, the cloaking system can help with this tactic. If the player is hiding, Barrett will slowly move about the room, calling for Jensen and throwing frag grenades into random locations. Using silenced weapons will not betray the player's position, though sustained fire is not recommended as Barrett will immediately turn and move in the direction of the shot.

It's worth noting that Barret is vulnerable to his own grenades. A good way to start off the battle is to throw a grenade to stun him and move to the right, where there are two gas canisters in the corner. Throw one can at him, wait a moment, then throw the second as he begins to move again. While he's choking the second time, run along the wall to the back of the room and hide behind the pillar there. Barret will search the area where he last saw you, and scatter grenades over the vicinity--and often catch himself in the blast. He may even kill himself doing this, or he may eventually widen his search pattern and get out of the corner and eventually wind his way to the player, albeit substantially weakened.

Using the Typhoon Explosive System/TES on him two times or three will kill him (on normal difficulty). Just be close enough for him to be hit by the detonation. But be warned-don't be so close or he'll use his deadly melee attack.

Give Me Deus Ex Difficulty

On Give me Deus Ex difficulty the easiest possible way to defeat Barret is, during one of the missions into Derelict Row there is an area that has 4 fragmentation mines in it. Sneak disarm them and keep at least 3 with you. In the beginning of the mission in the room with the large robot in it duck underneath one of the platforms and enter one of the vents this leads you to a room that has a rocket launcher and an ammo case of rockets pick it up. Before you enter the final room equip the rocket launcher and the frag mines, after the cutscene duck behind the wall right in front of you and shoot him once with the rocket launcher. While you are reloading toss a frag mine at his feet, he will walk straight into it. Shoot him again with the rocket launcher and throw a frag mine at his feet again while he is stunned. At this point he will most likely throw out 3 grenades, get up and sprint away behind one of the pillars. while in cover throw the last frag mine at his feet and the boss fight will be over.

Note: There is also one ammo case for the rocket launcher sitting on a crate immediately to the right when you enter the room. If you did not pick up the frag mines in derelict row there are two mine templates sitting in a crate in the room to the immediate left when you enter the room as well as a frag and EMP grenade.

Alternatively he can be killed without firing a shot or using a single mine/grenade by utilizing the 3 gas canisters and 3 explosive barrels in the room. As soon as the fight starts Jensen should back up a little and move to the left, where a few crates are located. Between the right and middle crate is a gas canister which should be thrown at the boss and will stun him. While he is stunned, move further left and grab the explosive barrel and carry it all the way to the right, where two more gas canisters are located against the wall. Throw the explosives, which will shake him out of the gas stun, but you can grab a gas canister right next to you and throw that, giving him no time to react and stunning again. Move across the room (behind the boss) to grab that explosive barrel, and bring it back to the remaining gas canister and repeat the process (explosives followed by gas), and then you can walk over to the last barrel which will end the fight. End result is a dead boss with no ammo used, and no damage taken.

Note: you can save your game midway through the encounter with Barrett, if you're doing well.