You have to kill the evil doctor and then chase the undead form he transforms into. When you catch up with him you do battle in an underground room with blood and gore covering the ground. A bunch of his zombies will start spawning during the fight so be careful. Aim for the head and he'll drop pretty quick. That'll unlock half of the hidden conspiracy items around the levels and you have to go find them. When you find them enter the codes on each one to unlock secret levels that you can find the guns in. To get the other half of the conspiracy items to show up you have to hunt down the big undead creature that the doctor created by sewing together parts from his two dead assistants, Frank and Bill. Enjoy and good luck :D
Playing: Borderlands, Golden Sun, Chrono Trigger Wanting: Golden Sun DD, Conduit 2, Starcraft 2, Civ5, Infamous 2, Brink, AC Brotherhood, and more Borderlands!