For Auld Lang Syne

 is a quest in Fallout: New Vegas.

Quick walkthrough
Talking to Arcade Gannon about his past will eventually reveal his history and the path he wishes to follow in order to aid the wasteland in the upcoming clash between the NCR and the Legion. He will take the Courier on a quest to reunite remnants of the Enclave in the Mojave. Gaining enough trust with Arcade will allow the courier to take this quest and help him resolve issues from his past.