 The dead bodies of badly beaten men are being found in the Boston metropolitan area. Sam and the team quickly surmise these men were involved in some sort of deadly, ultimate, bare-knuckle fighting match. Searching local hospitals, they find a participant in one of the fights. Sam is able to put together from talking to him and researching the backgrounds of the victims, that all were desperate men in need of money. All the men have a bookie in common and the team eventually gets this man to confess his role in the murders. To catch the fight s mastermind in the act, John goes undercover as one of the fighters.