Silus Treatment

Silus Treatment (or McCarran: POW in the G.E.C.K.) 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 enough, though the required Speech skill is not shown) will cause him to spill information.
 * This is worth 50 extra XP
 * 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 panicking, causing him to accidentally tell you all of his plans in an attempt to convince you into sparing him, as well as hinting to you about Caesar's illness, he will also hint about the spy Caesar planted in McCarran. Here, some knowledge of Latin will help you understand the dialogue choices:
 * Timeo Danaos et dona ferentes means "I fear the Greeks, even when they offer gifts." This is a line from the Roman poet Virgil, recounting the doubts of Laocoön, one of the Trojans, about accepting the gift of the Trojan Horse.
 * 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."
 * At the end of the conversation the player can attack him, asking if he has any last words, to which he replies "Cedo Nulli" which means "I yield to no one," though he does not become hostile.

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.

Killing Silus during the interrogation results in Boyd condemning your action by complaining that she lost her best shot at getting a promotion since he didn't reveal anything about the Legion and you ended his suffering, and finishing this diatribe by calling you an "asshole." An NCR Infamy gain is received.

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.

Rewards

 * NCR fame
 * 175 caps (attacking Silus) or 300 (persuading Silus) caps
 * 250 XP (attacking Silus) or 325 (persuading Silus) XP

Behind the scenes
The name of this quest is a play on the term "silent treatment," which means to deliberately ignore someone for a period of time, usually because of something they have done.