When a jackhammer at a construction site uncovers a pool of blood oozing from the ground, Mac and the team are called in only to find there is a man's dead body buried in the cement. The victim, Joe, is badly beaten and wearing a Gladiator costume. The team finds he was a former amateur fighting champion that had retired do to brain injuries. Joe was well-respected and had seemingly no enemies. Glass shards found in Joe's Gladiator armor are of a unique type of glass not available on the mass market and the manufacturer is able to lead the team to a vacant high-rise office space in Midtown. Blood evidence from the victim as well as many others at the office uncovers an internet-based underground amateur fighting ring that Joe was apart of. The owner of the internet site and the victim's former trainer, who was like family to Joe, joined forces to convince Joe that his brain injury healed and he should return to fighting solely for their own financial gain. When Joe was struck in the head during his last fight and began hemorrhaging, both men panicked and buried Joe at the construction site, neither knowing they were burying him alive.
Det. Flack and Danny inform Mac that surveillance footage of an ATM in the Manhattan area shows that Shane Casey tried to use Danny's canceled debit card (stolen by Casey's accomplice - episode #612) in the past few days. Mac knows that Casey is sending the team a clear message that he has returned to Manhattan for one reason only - Them.