Welcome to the Big Empty

Welcome to the Big Empty is the first main story quest in the Fallout: New Vegas add-on, Old World Blues.

Quick walkthrough

 * 1) Arrive at the Sink balcony.
 * 2) Take the elevator to the think tank.
 * 3) Agree to help the doctors.

Detailed walkthrough
After being teleported to Big MT, you will be standing on The Sink balcony. Enter the door behind you into the Sink, then proceed to the elevators. Enter the elevator on the right that takes you to the Think Tank. Due to an overwhelming feeling of pacifism, you won't be able to draw a weapon in the think tank. This is most likely so that you will not be able to harm the doctors. When you approach the doctors (who appear as floating brain computers), they will address you, and you will learn about The Big Empty, the various changes they have made to your body, and about Doctor Mobius.

After agreeing to help the Doctors against Mobius, they will give you the Sink Central Intelligence Unit.

Through various conversation options, you will be able to talk the doctors into giving you various items to help you in your quest. The doctors give you the Sonic Emitter - Revelation. With an Energy Weapons check of 50, you will be given more ammo for it. With a successful Guns check, also of 50, the Doctors also give you the K9000 Cyberdog gun. Other items include doctor's bags, stimpaks, bottle caps, and various skill magazines with a successful Barter check of 25, then another at 50.