Welcome to the Big Empty

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

Quick walkthrough

 * 1) Head to the Think Tank from The Sink.
 * 2) Agree to help the Doctors.

Detailed walkthrough
After being teleported to Big MT, you will end up in front of a door to The Sink. Enter the Sink, then proceed to the Elevators. Enter the Elevator that takes you to the Think Tank. 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 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 a successful Guns check, the Doctors also give you the K9000 Cyberdog Gun. Other items include Doctor's Bags, Stimpacks, and various skill magazines with a successful Barter check.