Silus Treatment

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough

 * Travel to Camp McCarran and enter the terminal.
 * Go to the west end of the second floor. Find Carrie Boyd in a room to the north.
 * Speak to Carrie Boyd and agree to help her interrogate the prisoner.
 * Interrogate the prisoner and get him to tell you about Caesar and the spy at the camp.

Detailed walkthrough
Silus is held captive in Camp McCarran, and the NCR is attempting to interrogate him. He will not give information to the NCR, and interrogator Carrie Boyd is looking for help. She informs the player that the NCR does not allow torture of prisoners. The player can suggest a truth serum, beating the prisoner, or calling him names.

If the player has a high enough reputation with the NCR, Lieutenant Boyd will allow the player to go in and speak with the Centurion. The player will go in unarmed, unless the player's sneak skill is high enough to bring in holdout weapons.

The Courier can either break Silus or help Silus escape.

Break Silus
The Courier can speak with Silus or attack him outright. Here, some knowledge of Latin will help you understand the dialogue choices:
 * Should the player speak with Silus:
 * Passing a speech check will result in the legionary attacking. After a brief fight, Lt. Boyd will come in again and ask Silus if he wants more. When the legionary refuses, the player will briefly speak to him again, and begin attacking once more. After a second round of fighting, Silus will talk.
 * Passing a series of speech checks with high speech (50 is certainly enough, though the required Speech skill is not shown).
 * With Intelligence 8 or higher, the player can persuade him into thinking that you are working with the Legion and are here to assassinate him; this will result in him telling you all of his plans.
 * Timeo Danaos et dona ferentis means "I fear the Greeks, even when bearing gifts." This is a line from the Roman poet-historian Virgil, recounting the doubts of one of the Trojans about accepting the gift of the Trojan Horse (often mistranslated as "Beware of Greeks bearing gifts").
 * Corruptio optimi pessima means "Corruption of the best is the worst possibility." It is originally from Pope Gregory I (Gregory the Great).
 * Legum servi sumus means "We are all slaves to the law." The phrase is originally from the Roman orator and statesman Cicero, and in full reads Legum servi sumus ut liberi esse possimus -- "We are the slaves of the law, in order that we might be free."

You can also kill Silus to gain history points with Boone. Just take Boone with you and give him a weapon like a knife. Enter the room, go through the speech checks, exit the room and talk to Boyd to get your reward. Take the weapon from Boone and kill Silus. Talk to Boone to advance your history with him and give him back the weapon and leave.

After the information is gained from Silus, you can no longer interact with him, and Lieutenant Boyd will pay you for your troubles.

Help Silus escape
If the player has already been invited to Caesar's camp at The Fort or have a positive reputation with the Legion, they have the option to tell Silus this. The player can choose to stage a fight with him and retrieve his silenced .22 pistol from the locker in the next room. When the player returns for the second round of interrogation, Boyd will confiscate all weapons except the pistol. After giving Silus the weapon, he will fake being unconscious. Boyd will come back in and say it looks like he is "all tuckered out", and she and the player will leave. On the way out, she will tell the corporal to go clean Silus up and he will go in and tell Silus to get up. Silus will kill the Corporal and dress in his clothes. He will then sneak out undetected by the NCR. The player will not lose any reputation with the NCR as a result.

Note: After Silus is dressed as an NCR corporal he will not speak to the player while he leaves.

Rewards

 * NCR Fame
 * 300 Caps
 * 325 XP

Bugs

 * You can earn infinite XP with a glitch while talking to Silus. Use the first speech check option (50 XP), then use intelligence one. After Silus' answer, you can use again the speech check and the XP. Do this as much as you want.
 * If you leave the room after the first time you talk to Silus, you can not get back in, and further interaction with Lt. Boyd only result in her saying "Let's talk after we finish this up" and ending the conversation abruptly. There doesn't appear to be any way into the room after this point. Though it is possible that you need to come back to the area in a few hours(game hours) to be able to get in again.
 * The door has many opportunities to bug - if you save after Boyd enters the room to introduce you (perhaps only as she is starting to walk out?) you will not be able to enter the room to interrogate Silus after she leaves. Also, if you decide you want to pummel Silus to death to earn points with Boone towards triggering his character quest I Forgot to Remember to Forget, Boyd may get stuck in the room afterwards, preventing you from talking to her again and completing I Put a Spell on You.
 * Reloading the auto save that occurs when you enter the room, may cause all your weapons to spawn back in your inventory.
 * ) Around the third going into the interrogation room, a random NCR trooper was inside as well, and he killed Silus, not allowing you to get the full reward and giving you infamy with the NCR.
 * sometimes Boyd's face may not load and will only have her eyes and mouth showing.NOTE: can be fixed by exiting the building and re-entering.
 * Do the speech option of [Intelligence] and don't leave the room. If you engage in conversation with Silius while Boyd is talking to him again, Boyd may disappear, although the conversation between her and Silus continues. If you tell Silus you are not from Caesers Legion while this happens, after Boyd finishes the speech you can talk to Silus again and apparently he just forgot what you said and thinks again that you are a legionnaire.
 * If you initiate this quest and have Boyd enter and talk to Silus but then you don't go in after she exits and you leave and proceed to do various other quests and gain rep with the NCR, when you come back you may be unable to continue the quest and Boyd will act as if you "have to do a lot more NCR ass-kissing" before she'll let you help with Silus. If you talk to Hsu, he will still recommend that you see if Boyd needs help.
 * After entering the interrogation room for a second time and beating Silus to get the information a glitch can occur when exiting the room to talk to Boyd. She will disappear and not be anywhere within the building.
 * If you equip any unarmed weapon (Boxing Tape, Bladed Gauntlet) that is not classified as a holdout weapon, it will appear on your character model, but won't actually be equipped. If you then leave the room and equip and other weapon, it will remain on your character model with another weapon in your hand.
 * After helping Silus escape, sometimes Lt. Boyd got stuck in the same dialog, making future interactions with her impossible. On the PC, this can be fixed in console with the command
 * If you do all of the science checks in Silus' dialogue then kill him before Boyd tells you to stop, Boyd returns to the room and lock it and will not leave but appear to be talking to the empty chair.
 * If you have ED-E as a companion, he can follow you into the interrogation room. Once you start hitting Silus, turning him hostile for brief periods, ED-E will also attack him.
 * After entering the interrogation room for the first time, re-load the auto save of when you entered the room. You should now have all your weapons not just holdouts.