Prime

Prime appears as a corpse at Dot's Diner near the Jury Street Metro Station, but only after you answer the 3 terminals in the Museum of Technology correctly. The three terminals are recognizable by the #001 #002 and #003 option at the bottom of the options menu upon entering each terminal. From the outside, the terminals look like any other computer terminals on the wall.

The first terminal, which is located in the museum's atrium, will initially have #000 for an option. When you pass that, it changes to #001 and the player can begin the treasure hunt.

The key to accessing the treasure are prime numbers. After the player selects the prime number from the other two information terminals in the Museum of Technology, the reward is a key to a safe in the museum. The player will then be told that Prime is waiting at Dot's Dinner near (but not inside) the Jury Street Metro Station. When you get there, you'll find the sweet Xuanlong Assault Rifle on his corpse.

There is also a possible encounter that will spawn Talon Company or Outcasts NPC. For my case, I lure those Talons to the Brotherhood and loot them after they finished "argument".