las vegas. every year, millions flock here. trying to fulfill a dream and win big. this is the las vegas the world knows, the casinos, the hotels and the clubs, but step off the strip and you'll find another world that couldn't be more different. a world where lost people hide in plain sight. this is crazy. in the middle of the desert. oh, my gosh. in boarded up buildings. wow, look at this place. even underground. it is pitch black in here. it's a world that can be dark, unpredictable and sometimes very dangerous. oh, someone's just coming out. >> could be a drug deal. could be anything. >> wait!