Silus Treatment

Silus Treatment is an unmarked quest in Fallout: New Vegas.

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 reputation of Accepted or higher 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.
 * Should the player speak with Silus:
 * The direct option is to attack Silus. After a brief fight, Lt. Boyd will come in again and ask Silus if he wants more. When the centurion 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) will cause him to spill information.
 * 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. Here, some knowledge of Latin will help you understand the dialogue choices:
 * Timeo Danaos et dona ferentis means "I fear the Greeks, even when bearing gifts." This is a line from the Roman poet 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 has 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 Courier will not lose any reputation with the NCR as a result.

Notes:
 * After Silus is dressed as an NCR corporal he will not speak to the Courier while he leaves.
 * If Boone is with the Courier, he detects and becomes hostile to Silus once Boyd has left the room and called for the Corporal. Silus also detects Boone and walks around with the pistol drawn. Silus ultimately leaves the room (and will typically be shot dead by Boone) without having shot the Corporal or disguised himself. Boone does not talk about the incident afterwards.

Rewards

 * NCR fame
 * 175 (attacking Silus) or 300 caps (persuading Silus)
 * 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 Caesar's 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 legionary.
 * 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.
 * Note: After experiencing this, it may be possible to find her through the I Put A Spell On You quest. She may appear in the hall to the right of where you find Col. Hsu, by the Nuka Cola machine.  This may require I Put A Spell On You not being started until after Boyd disappears.
 * 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.
 * Loading the Autosave when you enter the interrogation room may result in you being permanently locked inside with Silus.
 * If you do all of the speech 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 or Boone 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.
 * Silus must reach the terminal doors without being made hostile through a failed pickpocket attempt (even if he doesn't detect the player) in order for Caesar to acknowledge his release.
 * When interogating Silus, any characters inside the terminal, most commonly the Corporal or your followers, may believe that Silus is an actual threat and come to your aid, resulting in Silus' death.
 * Sometimes when Boyd enters the room where Silus is located, she may not exit the room making the quest impossible to complete, this may be fixed by continuing other quests.
 * If Silus killed the trooper that arrives to pick him up, he might get stuck walking into a wall. To fix this, just wait a hour and he'll have disappeared.