Picking Up the Trail

 is a Fallout 3 quest. It is also a Xbox 360/PC achievement and a PlayStation 3 Trophy.

Summary
Picking up the Trail consists of finding and gaining entrance to Vault 87.

Talk to Scribe Rothchild
Scribe Rothchild can usually be found in the laboratory area of the Citadel; once met, he will reveal the location of the Citadel's Vault-Tec terminal. Alternatively, you can bypass this conversation by going straight to the computer.

Once you've consulted the terminal, Rothchild reveals the location of Vault 87 and briefs you on the difficulties involved in accessing it, suggesting you explore a possible entrance within Lamplight Caverns.

Lamplight Caverns

 * See also: Little Lamplight, Rescue from Paradise

Once you've arrived at Lamplight Caverns, Mayor MacCready will stop you at the gates of Little Lamplight. You can convince the mayor to let you in with a Speech challenge or with the Child At Heart perk. Failing that, the only way into Little Lamplight is to complete the Rescue from Paradise side quest.

Once in Little Lamplight, there are two ways to get to Vault 87:
 * 1) Passing through Super Mutant infested Murder Pass; if you chose this option, you must first speak with Mayor MacCready or Princess to get the gate to Murder Pass open.
 * 2) Asking Mayor MacCready about alternate paths will reveal a locked back door to Vault 87. You must ask Joseph to restore power to the computer terminal before you can use it. The door and terminal (average difficulty) are located in the Great Chamber.

Bugs

 * If Princess is located near Murder Pass when you convince MacCready to open the gate, there is a chance that she will become stuck in the closed gate, preventing MacCready from opening it. If this happens, the only way to continue is to take the alternate route through Joseph.
 * It's possible that this quest will be considered "completed" and move you onto the next quest before you get into Vault 87.  This can be a problem if this occurs before you ack MacCready to open the gate to Murder Pass and/or Joseph to restore power to the computer console, as the dialog options that prompt them to perform these tasks are no longer available after the quest is "completed."  Thus there is no way into Vault 87 at this point by "playing by the game's rules."  In the PC version, however, one can use the console command "fcl" to switch off collisions, which will allow you to simply walk through the gate blocking the way to Murder Pass.  Once on the other side of the gate, use the "fcl" command again to re-engage collisions and then proceed on into Murder Pass.
 * Scribe Rothchild may disappear from the Citadel, resulting preventing the player from being briefed and advancing the quest. This can be fixed by using the console command 'player.placeleveledactoratme 000156ea'.
 * Talking to Rothchild when he is in the A Wing instead of the Laboratory may result in a bugged and broken quest. Making him unconcious by shooting him can sometimes fix this.( Confirmed Xbox 360 )
 * If you get into the Citadel (through the underground Glitch) you can start this without even doing "following in his foot steps" by Going to the archives in the citadel and looking at vault 87's Information.
 * In some instances Rothchild will tell you to follow him then make no effort to move, even under duress. Reload and approach Rothchild at a different time of the day--preferably when an NPC is talking to him and his back is turned--then begin the dialogue again. (PS3)

YouTube Videos
Fallout 3 Quest Picking up the TrailThumb|Left|Picking Up the Trail Thumb|Right|Picking Up the Trail