Old World Blues (quest)

Old World Blues is the final main quest in the Fallout: New Vegas add-on Old World Blues.

After completing this quest, the player will earn the Make up Your Mind achievement/trophy and the Outsmarted achievement/trophy upon completion of the entire storyline.

Quick walkthrough

 * 1) Talk to Dr. Klein.
 * 2) Enter the Forbidden Zone Dome Entrance.
 * 3) Defeat or disable the X-42 giant robo-scorpion.
 * 4) Enter Mobius' lair and reason with or kill him.
 * 5) Reclaim your brain.
 * 6) Reason with or defeat the Think Tank.

Detailed walkthrough
The player starts the quest by speaking to Dr. Klein, where the good doctor will tell him/her that it's time he/she went to the Forbidden Zone and get his/her brain back. He also asks the player to deal with Dr. Mobius. Optional speech checks are available:
 * Lockpick 75.
 * Repair 75
 * Science 65
 * Sneak 45
 * Then either Science 85, or Medicine 85.

The player should start by traveling to the Forbidden Zone. There the player will encounter a few robo-Scorpions. After dealing with them and entering the zone itself, Dr. Mobius will release his most powerful guardian, the X-42 giant robo-scorpion.


 * The player can fight it.
 * Enter the room farther to the right with stairs that lead to a terminal, which gives the player the option of activating the X-42 backup generator, overloading it and causing some damage.
 * Enter the room to the right and use the terminal to access turret controls (Average lock) to turn them upon the X-42 giant robo-scorpion. Although they will not be sufficient to destroy the X-42, they cause it a lot of damage.
 * Activating the Protectrons in the room to the right from the dome's entrance will distract the robot long enough to get to the shutdown terminal or other terminals.
 * Enter in the balcony room in the far left side of the zone from the entrance, that contains a computer terminal (Very Hard lock). If hacked, it gives the option to permanently disable the X-42 giant robo-scorpion. Access to this room is via the stairs in the far left side of the room. If the player lacks the necessary science skill the password to the computer is on a holotape to the right of the rightmost protectron bay.

Alternatively, if the player has the Robotics Expert perk, he/she can sneak up and disable it but the X-42 giant robo-scorpion will restart itself after a set amount of time has passed. However, if he/she does not have the required Science level to hack the terminals, nor the Robotics Expert perk, a LAER is available behind a forcefield, just past the exit balcony. This LAER is in good condition, and it can be sufficient to take out the X-42 giant robo-Scorpion.

After defeating it, the player must confront Dr. Mobius. To do so, he/she will simply need to take the stairs to the left of the entrance and make his/her way to the door on the right. There the player will meet Dr. Mobius, who, strangely enough, is not hostile.

Here the player has two choices: reason with him or kill him. If he/she chooses the former, he'll direct him/her to his/her brain and ask to convince it to rejoin the player. Optional speech checks are available with Mobius: a Repair 75, then Science 50, then Speech 65, then Intelligence 7, another Intelligence 7. Then either a Perception 7, a Medicine 65, or a Guns 75, then a final Intelligence 7.

The player must then speak to their brain, and convince it to join him/her again. Having high Medicine, Speech or Science will give him/her a slight advantage and make the dialogue much easier. Use of the unique dialogue provided by Confirmed Bachelor/Cherchez La Femme will result in a somewhat humorous, if mortified response from the brain that doesn't help the player's case. Two of the optional checks are both Speech 75. Talking to the brain and convincing it to help in the final quest stage will grant the "Make up Your Mind" achievement/trophy.

After acquiring the brain, the player needs to speak to Dr. Mobius again. He'll tell him/her more about what the Think Tank is all about and suggests dealing with them, instead of him. The choice is up to the player.

After making the choice, the player needs to travel to The Think Tank. There he/she has the option of using the Sink's Auto-Doc to retrieve his/her original heart and spine. Then it's either violence or reason. In order to reason, one must have:
 * Either 75 in Speech, 85 Medicine and/or 100 Science.
 * If the player's completed the side quests What's In A Name?, On The Same Wavelength, A Brain's Best Friend and Coming Out of Her Shell, he/she can tell Klein to confer with his colleagues and the others supported the view of the Courier, which allows the player to reason with the Think Tank without using the high skill checks.

After completing the quest, and watching the ending slide show, the player is given the Big Mountain Transportalponder!. This will allow one to return to the Big MT via The Sink balcony at any time. Furthermore, upon completion, all active personalities in The Sink will cheer for the Courier's victory, with a particularly drawn-out and rambling congratulations from Blind Diode Jefferson.

After the slide show ends (and the player convinced the brain to come back) the brain will be located in the far left room (where the heart and spine have been stored). The player will then be able to re-attach and detach his/her brain later at any time or leave it in the storage facility.

Journal entries
¹ Optional depending on speech paths taken during initial confrontation.

Bugs

 * When the brain is asked if it wants to be reunited, and then choosing the compromise option, the second choice, if the player has completed Come Fly With Me and That Lucky Old Sun, will result in a never ending loop of the brain talking about the quests.
 * Before entering the Forbidden Zone Dome, it is advisable to make a new separate save as when entering through the main entrance into the arena with the Giant Robo-Scorpion, it is possible to load under the catwalk and become stuck there.
 * Be mindful before completing the quest and make a save somewhere outside the Think Tank. When the quest is completed and the player is asked to leave Big MT, the moment the slide show starts the game crashes. This forces the player to reload an earlier save. If the last save is inside the dome, they will be trapped.
 * After finishing this quest by either killing, or talking to the Doctors in the Think Tank, the game may crash as the player tries to leave.
 * The game may crash as the slide show ends, on the last slide with the Old World flag in the foreground and a sunset in the background, when the screen begins to fade.
 * When speaking with Dr. Klein at the end of the DLC, some dialogue may repeat when the other brains are trying to keep the player alive.