S2, E8: When the unearthed remains of Mason Roberts, a federal prosecutor who disappeared five years earlier, are discovered in the desert outside Las Vegas, Brennan and Booth suspect his death may be tied to the mob. The body count in the desert rises when vultures lead them to the recent remains of a young woman, just a few yards away. Booth suspects the same person may have been responsible for both deaths, but the woman's injuries lead Brennan to believe she has a long history of domestic abuse and her husband may have been responsible for her demise. Brennan and Booth question the deceased woman's husband, who denies he hurt his wife, but leads them to a Vegas loan shark. When an anonymous lead takes them into the world of gambling and underground ultimate-fighting, Booth and Brennan go undercover as Vegas high-rollers. Booth takes his turn in the ring and risks his life in a desperate effort to undercover the mystery.