For Auld Lang Syne

For Auld Lang Syne is a companion side quest in Fallout: New Vegas.

Synopsis
While the Enclave has been nearly wiped out in the West, the remnants of the Devil's Brigade have survived in the Mojave. Arcade believes that they can aid in the fight against the Legion and asks the Courier to find them all.

Walkthrough

 * To start this quest, the player needs to enter Arcade's confidence by scoring 5 "points" with him:
 * 1 point can be gained by traveling to the crashed Vertibird, inside the REPCONN headquarters, and at The Fort.
 * The Fort conversation awards 2 points for saying, "Let's just listen to [Caesar], figure out what he's up to, and get out", 1 point for saying, "I just want to hear Caesar out." and 1 point for saying, "With how messed up New Vegas is, do you really think Caesar has nothing to offer?", followed by, "I'm just trying to be open-minded." It's possible to lose Arcade permanently at this point.
 * Up to 2 points can be gained by speaking to Thomas Hildern. Arcade will ask the player for his opinion on Hildern. 2 points are gained by saying, "Good thing there are still people like you around." and 1 point for saying, "I'm sure he means well."
 * 1 point can be gained during That Lucky Old Sun, when Arcade suggests that the power should be directed to Fremont and Westside. 1 point is awarded for agreeing with him or by suggesting to divert power to the whole region, and passing an Intelligence 7 check.
 * Several points can be gained during The White Wash:
 * 1 point for saying, "If you say so. I'm not arguing." when Arcade mentions that he's heard about Anderson.
 * 2 points for completing the quest by blaming the problem on the Scorpions and letting Tom Anderson go.
 * 1 point for completing the quest by getting Tom Anderson to turn himself in with a fake story about fighting over Dazzle, thus letting Westside Co-op continue to siphon the water off from the NCR.
 * 2 points for killing Anderson and passing an Intelligence 7 check by saying, "You're assuming a motive without evidence. Please be rational." when Arcade blows his top, and another by saying  "It's cleaner this way, without bringing NCR in. No connecting Anderson back to the locals.".
 * The quest will not start until the player reaches one of the following storyline milestones:
 * Destroying the Brotherhood of Steel during The House Always Wins V.
 * Installing Yes Man into the Lucky 38 mainframe during Wild Card: Change in Management.
 * Reporting to Colonel Cassandra Moore that Mr. House has been killed during For the Republic, Part 2.
 * Arcade will reveal that he has stayed in touch with his father's old squad and suggest that their firepower can help tip the battle against the Legion. He will ask the player to the remaining squad members, the Remnants. These are:
 * Doctor Henry in the main lodge at Jacobstown.
 * Cannibal Johnson in his cave.
 * Judah Kreger in Westside.
 * Orion Moreno in his house near the NCR sharecropper farms.
 * Daisy Whitman in or near her hotel room in Novac.
 * Each will give the player their part of the password to the Remnants bunker to the northwest. After all five have been asked to come, the player can access the bunker. They will meet in the situation room adjacent to the hangar, where the player can ask them to fight for the New California Republic or Caesar’s Legion during the Second Battle of Hoover Dam.
 * If the player asks them to fight for the NCR, Moreno will leave in disgust. He will don his armor and declare that he won't do it at all. The player can convince him to fight with a high NCR infamy or a Speech check of 80.
 * Selecting the Legion will result in Kreger, Johnson, and Arcade abandoning the Courier permanently.
 * Upon exiting the bunker, Arcade will meet the player, wearing his father's Tesla advanced power armor and ask for guidance: Should he pretend to be his father and fight alongside the Remnants at the Dam? Or trust his instincts and help the people of Freeside during the battle? The player's choice determines his ending.

Reward

 * The player will receive Power Armor Training for completing this quest, one of only three quests to grant it (the other are Eyesight to the Blind and Tend to Your Business, tied to the Mojave chapter).
 * Remnants power armor, as Daisy doesn't need hers to pilot the 'bird.
 * Completing this quest will result in the Enclave remnants fighting for the chosen side at the battle.
 * If they fight for the NCR, they will deploy at the rim and engage a contubernium of up to six prime legionaries and centurions. Kreger and Moreno (if present) will hang back, while Doctor Henry and Cannibal Johnson will assist the player all the way up to the Legate's camp. If Brotherhood of Steel Paladins and Knights assist the Republic, they will not be hostile to the Enclave.
 * If they fight for the Legion, only Moreno and Henry will deploy and attack the NCR troops.
 * If the player suggested that Arcade fight at the dam, he will present in the visitors center, assisting two heavy troopers.

Behind the scenes

 * The name of the quest is from the poem and song "Auld Lang Syne", traditionally sung on New Year's Eve. The title can be loosely translated from Scottish as "For Days Gone By", or "For Old Time's Sake", referring to remembrance.

Bugs

 * It is possible to complete the quest, without losing Arcade as a permanent companion. If he's told to wait at the Lucky 38 after recruiting the Remnants, but before entering the bunker, he will remain there upon return. Doing so breaks his scripts, however, and no ending will be displayed for him and the player will miss out on the power armor. The only ending available will be to sell him into slavery during Et Tumor, Brute?
 * The Remnants can randomly turn hostile at the Dam if the player sides with Mr House or Yes Man.
 * Receiving the power armor training from the Brotherhood can break the script for the quest, skipping over dialogue that awards the player Daisy's power armor.
 * The script to unlock the briefing room at the end of the quest can misfire and not unlock it after dealing with Moreno. The player can steal it from him to open it.