Dealing with Contreras

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough
There are two ways to complete this side quest. The first, and much quicker way is to hack his computer, (Average, 50 or more Science skill needed, or 30 if you wear the Followers lab coat and read the Programmer's Digest magazine) if you download the weapons manifest then report back to Lt. Carrie Boyd. The longer way is to speak with Contreras, he wants you to run several errands for him. Either will get you a unique rifle This Machine. There is also an opportunity to make a lot of caps if you are planning on turning Contreras in to the NCR.

Detailed walkthrough
Contreras can be found in the Supply Shack at the back of the terminal building via the concourse at Camp McCarran. Enter the terminal, go up the escalators, down the hallway to the concourse. When in the concourse bear left to a down ramp, and bear right to the door of the supply shack.

Quick Quest End:

The quickest way to complete this is to go upstairs in the supply shack, hack his terminal, download the weapons manifest then report back to Lt. Boyd with your findings. She will reward you with This Machine and you will receive NCR fame.


 * Hacking his terminal will give you bad Karma for each attempt you make at hacking it.
 * Using this method will result in Contreras being arrested, thus eliminating him as a source of weapons and ammo, though there is an item unique to Contreras, which is Ultra Jet.

There is a great opportunity to make a lot of caps, get some decent gear, or both if you are planning on turning Contreras in to the NCR. After hacking his terminal upstairs, proceed downstairs and open up the barter menu with Contreras. Then proceed to sell Contreras everything in your inventory, but make sure you keep at least one powerful weapon that you are skilled with. If Contreras has any gear you like then go ahead and get it. The goal here is to try get as many caps, weapons, and/or armor from him as possible.

After you have finished selling him all your stuff, pull out the powerful weapon you saved and kill Contreras with a sneak attack. You will receive no bad karma for this and the NCR does not react badly to this action. After killing Contreras go over to his body and use the "take all" option. You will get everything you sold him back. Make sure you take everything off his body because you will lose anything you leave behind when you complete this quest. If you become over encumbered simply put some of your stuff in one of the lockers and come back for it later. By doing this extra little step, You can potentially make 6,000+ caps plus some weapons or armor at no cost to you. Try to have two followers with you before doing this ending to the quest. You can fill both their inventories with high value guns, armor or whatever before talking to Contreras. This gives you triple the amount of items to sell thus increasing your return in caps and gear. You can also buy everything he has, potentially 40,000 caps worth of stuff (if you are carrying that many caps), then use a stealth boy to pickpocket all your caps back. You can then go sell all the stuff you got somewhere else. Be sure to save before trying this in case something goes wrong.

Next, go talk to Lt. Boyd and give her the weapons manifest. You will still receive positive NCR fame and she will still reward you with This Machine.

Keep Contraras & finish his quests: If you want to keep Contreras in the game as a merchant, and want a longer quest, then speak with him. You need to be at least level 12 before Contreras will give you the dialogue option. After talking with him and passing a speech check of 50 or paying some caps, he will send you to find Isaac at Gun Runners.

Isaac is normally at the work bench at Gun Runners. You must either pass a speech check of 80, or a barter check of 80 or collect 100 pieces of junk metal (tin cans, bent tin cans, metal pots, pots, pans and scrap metal although it is advised to just give Isaac trash and save the scrap metal for your weapon repair kits) for Isaac before you can return to Contreras.

Several locations offer plenty of free Tin Cans and Bent Tin Cans that do not require theft/karma loss. They include the basement of the REPCONN Test Site, The same room as the Ratslayer in Broc Flower Cave, the porches of Nipton Road Reststop, inside Allied Technologies Offices, and in Jacobstown (many rooms within the main lodge, and inside the bungalows). If, however, you do want karma loss to come along with your tin cans, there are plenty to steal in the Concourse of Camp McCarran, and in Aerotech Suite 200.

If Isaac does not appear at the work bench, go to his house to the east of Gun Runners. He will be in his house or will usually appear as you exit the house, and will run to the Gun Runners kiosk location.

After delivering the scrap to Isaac, return to Contreras and he will reward you with caps and your next mission, which is to pick up some "medical supplies" from Blake at Crimson Caravan (with a high enough science or medicine(lvl 25), the player can identify the "medical supplies" as materials for making drugs). Return to Contreras who will pay you and tell you to wait a day or two for the next mission. You can just Wait for 24 hours and then for another 18 or so hours and then try him again.

He will direct you to deliver the "medical supplies" to Price at Miguel's Pawn Shop. When you arrive you will find he is not there, instead talk to Keller and offer him the passphrase instructed in your last meeting with Contreras. Keller does not know the counter-phrase. As always in this game, there a number of paths you can take.

-You can just say goodbye and report back to Contreras. -You can just go with it and try to initiate a conversation with Keller regarding the package delivery from Contreras. Keller will then reveal that he is an undercover NCR Ranger and then attempt to arrest you. Choosing the latter you must then choose to:
 * Kill him
 * Bribe him (250 caps)
 * Or, with a Perception stat of 7, help him arrest Contreras.

The option to give the evidence to Keller will only get you arrested and force you to attack Keller. If your stat is not high enough and you do not want to end Keller's life, then take the first option and say goodbye and report back to Contreras.

In any case, return to Contreras with the news. If you killed Keller, Contreras will reward you with the unique rifle "This Machine"; otherwise, you must go back and kill the ranger or you can change your mind and help him "deal with" Contreras. On the other hand, if you bailed and returned, then Contreras will encourage you to return to Keller and murder him in order to stifle the NCR investigation.

At this point you can make a 80 Speech check or 70 Barter check you can convince Contreras that you can make a deal with Keller, or a 50 Barter to convince Contreras it will cost him some more money if he wants you to kill Keller. When you return to Keller a 80 Speech check is required to get him to work with Contreras. If you follow this path through though you will not get This Machine.

Before going out the door of the Supply Shack, go upstairs, hack the terminal (average), and download the manifest therein contained. You will need this evidence later.

Assuming you want to stay in the good graces of the NCR, return to Keller and follow this path: -First challenge Keller with the fact that you know he does not work with Price. Unhappy that he has been exposed, Keller will then explain that he is an NCR Ranger investigating Contreras and that Price is now being questioned regarding his role in Contreras' scheme. -Next, explain that you are just a bagman with instructions to kill Keller. This will raise Keller's spirits as this is just the evidence needed to arrest Contreras. You can attempt to bribe Keller here, express concern over Contreras' fate, or throw Contreras to the wolves. If you do the latter, Keller instructs you to return to Lt. Carrie Boyd and so bring the investigation to a close.

With a good sneak skill and a silenced weapon (sniper rifle suppressor works fine) you can kill Keller without any NCR fame drop. Stand in the left corner of the shop and take Keller out with a headshot, this solution give you This Machine from Contreras and also upgrade his stash in his shop. When returning to Contreras you will get the speech option "I convinced the Ranger to work with you. You're safe, but be careful." even if you killed him. You will get This machine and your NCR reputation will remain unchanged from what it was before starting the quest.

If you choose to help Keller, talk to Lt. Boyd and the quest will end, which will get you the same rifle, "This Machine". There is no option to talk to Lt. Boyd about Contreras unless you have hacked the Supply Shack terminal and downloaded the manifests that Contreras has on it, or confronted Contreras about him making chems (confirmed for taking bribe from him) proving his guilt. Only then will you get "This Machine". You cannot choose to help Keller, and he has no control over the quest reward. Contreras will be moved to the Prison Cell Block, directly opposite from the room that Silus (Legion prisoner) is kept. Contreras can still be used as a merchant but his inventory doesn't get replenished. If you hack Contreras' computer and then talk to Lt. Boyd, Contreras loses all of his merchant inventory although still functions as a merchant.

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Bugs

 * Sometimes your contact for the third errand will not show up.
 * The responses for the third errand are all messed up if you choose to kill the officer first.
 * After the third errand he will disappear and won't be where you previously talked to him.
 * When you first speak to Contreras there will be no option to start the quest, just to browse his inventory and to leave.
 * Isaac may disappear from the game.  Isaac may get stuck in his house and stop appearing near the Vendortron.  Go look for him in his house (I believe E-SE of the Vendortron, check local map).
 * Isaac may also be killed by Fiends while going to and from his home and the Gun Runner's kiosk.
 * After delivering the medical supplies/chems, when Contreras tells you to 'come back in a few days', you are given the dialogue option to say "So where was I supposed to meet Price, again?" even though you haven't been given that part of the quest yet.
 * Third Errand: If you pass the 70 barter check with Agent Keller before convincing Contreras to work with the Ranger, Keller will tell you to go back to Contreras and offer him the deal, but Contreras will have no more dialogue options, and the player will be locked out of completing the quest and receiving "This Machine".
 * Workaround: If you choose to just kill Keller at this point, the dialogue option to get "This Machine" should still become available. He can be killed stealthily without gaining NCR infamy.  Talking to Boyd does nothing, as there is no longer an option to rat Contreras out after making the 70 barter check deal with Keller.
 * Even with 7 or higher perception, the speech challenge which results in you helping Keller arrest Contreras will always fail, since the perception check is run on Keller instead of the player.
 * The dialog when you give Contreras up freezes the game.
 * After the quest is completed and Contreras is locked up in one of the cells, it is possible for you to initiate dialog with him (via 3rd-person view) and browse his wares. However, the game will freeze upon exiting the buy/sell screen.
 * Contreras after completing the third task and obtaining "This Machine" will still sell to you, but will not give you the goods you purchase, but will gladly take your caps.
 * After he turns over This Machine and allows you to purchase from him, any attempt to trade with Contreras results in the game freezing upon exiting the bartering screen... making you wish you just turned him in to Lt. Boyd.
 * Sometimes when given the medical supplies, they can be sold and lost forever; making it unable to get This Machine.
 * The medical supplies can sometimes stay in players inventory even after delivering them to Contreras.
 * If Contreras sends the player back to kill Keller, and the player does, upon returning to Contreras the dialogue prompt will read, "I convinced the Ranger to work with you." Regardless, the task will still complete, and Contreras will still reward the player with "This Machine".
 * Contreras' claims that if the player completes his last task, he will give the player "full access to my stash. At a discount, even", however there is no discount from Contreras ever offered, no matter how you resolve things.
 * When attempting to sell Contreras your equipment, upon exiting the buy/sell screen, the game with crash and require a hard reboot.
 * Lt. Boyd is apparently part of the First Recon unit. If you complete the headhunting quest given by Major Nephi before you complete this quest, she will leave with the rest of the unit and not be available.