The residents of the Mojave have long assumed the trackless wastes of the ‘Big Empty’ are a no-man's-land, a desolate stretch where no living thing can survive. In Old World Blues, you discover that it is anything but...

After being transported to the Big MT research crater, you find you're the only hope of saving the Think Tank – the strange group of post-human researchers who inhabit the facility. They enlist your aid to save them from their own experiments - experiments that have gone horribly out of control. As you explore the huge stretch of the Big MT crater and its many underground labs, you’ll confront strange mutated animals, battle terrifying new atomic robots, and discover a new home base to call your own. Recover all the weapons, armor, and tech of the Pre-War era and use them to help save all of Science!

• New Terrain
  Explore the expanse of the ‘Big Empty’ and its huge variety of research centers, arboretums, canyons, and scientific labs. Even better, find and upgrade your own home base, the Sink, within the Big Empty's central dome!

• New Enemies
  Confront the surgically-altered Lobotomites, bizarre robot scorpions, the dead occupants of the Y-17 Trauma Harnesses as well as the terrifying disembodied brain, Dr. Mobius. Look out for other strange and terrifying creations of the Think Tank!

• New Perks and Weapons
  Old World Blues increases the level cap by 5 and introduces a range of new weapons including the Sonic Emitter, K9000 Cyberdog Gun, Proton Axe, and several varieties of Mad Scientist Gloves such as the Sterilizer Glove and Corrosive Fist.

  You’ll also find new armors such as the Sneak Suit and Mad Scientist Scrubs to make your life in the Mojave easier. Look out for implants that can switch your body parts in and out for new effects and defenses to aid you in the Big Empty and the Mojave wasteland!

(Official site)