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) End up in a room with a lot of tech.
 * 2) Head to the think tank from the Sink.
 * 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 Tanks. Due to an overcome feeling of pacifism, you won't be able to draw a weapon in the Think Tank. When you approach The Doctors (who appear as floating brain jars), 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(50) check, the Doctors also give you the K9000 Cyberdog gun. Other items include doctor's bags, stimpaks, and various skill magazines with a successful Barter check.