- slide 1 of 2
Investigating Contreras - Introduction
If you don't plan to help Contreras with his crooked deals, then this quest is actually quick straightforward. You should be able to find out about it during the "I Put a Spell on You" quest. If you talk to Carrie Boyd, she should mention that she's noticing a lot of Contreras' inventory reports coming up light.
This isn't an official quest on the "good" side, so you'll need to take your own initiative and do a little hacking.
You can find Contreras at the back of the main concourse at Camp McCarran. You basically need to look for what amounts to a small shack at the rear of the base. It can be reached through the back of the airfield or the rear of the terminal. Contreras spends most of his day in the middle of the storage room. He should actually admit to his crimes immediately and offer himself up as a merchant. On that note, he's a pretty good merchant with a good supply of ammo. You may want to check out his wares before you finish up the quest. Naturally, if you take this path he'll no longer be able to supply you.
- slide 2 of 2
Investigating Contreras - The Evidence
There seems to be only one clear way to get the evidence necessary to prove Contreras' guilt. Even if you follow his questline, the option to betray him still seems to require that you get his inventory list. This inventory list can be found on the computer in the storage room. It's located above the spot where Contreras usually stands. In fact, you should be able to stealthily hack it by just crouching and waiting a moment.
In order to hack this computer, you'll need 50 points in your Science skill. Obviously you can use a Programmer's Digest magazine, if you want to speed things up a bit, but otherwise you will probably just need to wait until your skill is that high. As a mentioned, this is basically a shortcut to an amazing rifle, so it's only logical that there is at least a minor obstacle.
Once you hack Contreras' computer, you should be able to read the inventory list and confirm his theft and smuggling operations. Once this is done, you will automatically download the list. Don't bother talking to Contreras. Just walk back to the front of the terminal and find Lt. Boyd in her office.
You should have a conversation option that informs her of Contreras' actions. You'll hand over the evidence and she'll send some MPs to arrest Contreras. As I mentioned, he will not be available as a merchant after this point. You can see him in a jail cell close to Boyd's office, but he doesn't have anything to say. As a reward for solving the thefts and catching Contreras, Boyd will give you "This Machine." This is an amazing rifle and is perfect for fighting the Fiends around Camp McCarran. It also uses .308 ammo, which is pretty easy to find. A great weapon for the middle of the game.