On what should have been a night like any other, the last thing Vasco Ruiz sees as he draws his final breath is the ceiling of a dark, empty parking structure. A dishwasher at the hotel, Vasco was a family man who did nothing to provoke the violent attack. After the CSIs arrive, Catherine wonders what was used to kill him. "A blender?" Brass quips. It looks like a robbery gone wrong, but the intensity of the injuries says something else to Brass. Grissom finds Ruiz's car keys in the garage, but as he checks it out, police cars at the scene race away to another crime.
It's another attack: this time a young woman walking to her car was jumped by a man wearing a pig's mask. Luckily, the woman survives, but she's got no ID and is unable to talk. Nick figures she's probably a tourist who didn't know that the Vegas strip isn't as safe as it seems.
At the hospital, Sara photographs the recovering female victim, Jessica Hershbaum, who's battered beyond recognition. She just wanted a vacation after a tough break-up, and this was her reward. She has some good information for Sara though; she heard the culprits say she was number two for the night.
As she's taking evidence, Catherine finds a brightly painted toenail in Vasco Ruiz's mouth. She and Greg work together on tagging the shoe patterns on the both the victims' clothing. They find at least five separate shoe prints. Might be a hate crime, considering one victim was Hispanic, the other Jewish. "Looks like hate to me," Greg agrees.
Sofia interviews a liquor store owner whose shop has been hit hard by the gang of thugs. They took loads of high-end alcohol, but at least the irate owner escaped with his life. While he was able to grab a sweatshirt off of one of the perps, he didn't see anything else. Except… one of the guys had a disfigured nose, which creeped him out.
Sara finds two matches to the shoe prints in the SOLEMATE database, one for a Chuck Taylor, the other for a Doc Marten. Brass talks to Vasco's devastated wife, who's got two children to feed and no hope for the future. He takes Vasco's cell number to check his records, but by all accounts, Vasco was a good man with no enemies. As Brass passes a television in the waiting room, he watches a news report about Jessica's beating, including amateur camera phone footage of the entire attack. "Get this reporter on the phone," he tells a uniform standing nearby.
Greg's had a great day so far -- he made his first ever court appearance in a slam dunk case. Now he's headed out to the liquor store to bag the sweater evidence. But his good day is blown to bits when he happens upon another attack in progress. Though he's instructed by dispatch to wait for backup, Greg knows the victim doesn't have time, so he races his car down the alley flashing his red lights. That's enough to scare off most of the perps, except one young man wearing creepy contacts in his eyes. The man rushes Greg's car with weapon in hand, and Greg hits the gas and smashes into him. For a moment, he's alone, until the gang descends upon the SUV, breaking the windows and dragging Greg to the ground. They beat him incessantly, spitting on his jacket. Finally, they leave him alone in the street, dazed and bleeding.
When Sara arrives at the scene, it's already morning, and Greg has been stabilized. Carefully he tells her which evidence to process: skin cells under his nails, saliva on his jacket, paint transfer on the Denali. She's going to process him, while Nick and Warrick work the scene. The guys are soon interrupted by a couple of hecklers, one of whom gets under Nick's skin so badly that Nick throws a punch right into his gut. Warrick has to hold Nick back, and when Warrick threatens the heckler with a little investigation, the guy backs off.
Later, Grissom visits Greg, who's suffered extensive injuries. Greg asks about the two victims, one he saved, the other he hit. The original victim, Stanley Tanner, will be fine, but the other, a university student named Demitrius James, might not make it. When Grissom wants to call Greg's parents, he balks; he hasn't even told them he's out in the field. His mom was always overprotective, and she'll be devastated at his injuries. "Now would be the time to come clean," Gil advises. He saved someone's life, and she'll focus on that.
Catherine questions a young woman, Cha Cha Romero, whose cell number matches that of Vasco's last cell phone call. It wasn't Vasco, but rather a friend of Cha Cha's named Tara, who made the call to tell her to come out and party with her and her boyfriend, "Pig." They go out "fannysmackin'" on the weekends, beating up fannypack-wearing tourists for fun. This is the first time Cha Cha has heard about anyone dying from it.
Brass and Sofia run into a couple of loud-mouths at the PD who do their best to convince the cops that they've been robbed of 10 grand by the roving gang. Sofia and Brass are skeptical, since one of the men, Dean Harden, is walking and talking without any problems. He's only a little beaten up.
Cha Cha's friend Tara gets picked up at her home, and as she's carted off, Nick checks out paint transfer on her red coupe. He glares at her as he takes a wallet from inside the car. It's Vasco's.
Hodges processes the sweater from the liquor store for DNA, but there's no match to any of the perps. Same goes for the EPITHELIALS and saliva from Greg's case. Hodges and Grissom inspect the map of the crime scenes, and Dean Harden's is the one that doesn't belong. It's nowhere near the other four crimes, and besides, there's only one shoe tread on his clothes. Conveniently, it matches his own shoe.
When confronted with the evidence, Dean caves. He owes money to a sports handicapper and needed a fast way to make the 10 grand. But the idea backfired; now he owes the 10Gs to the infamous Uncle Lenny, plus another thousand to the Vegas PD for filing a false police report.
Nick and Catherine decide Tara is the best way to get to Pig, the king of the roving gang. Under pressure, she writes a text message that will lure Pig to a familiar spot, while Catherine and Nick text the rest of the people on Tara's phone to meet at the same location. They all drive into an abandoned warehouse, only to be surrounded by another swarm: the police. They're armed to the teeth. The Pig Man gets taken down by a shotgun-toting Sofia. It's the guy who heckled Nick at Greg's scene. He snorts and sneers at Nick as he's taken away in a prowler.
Stanley Tanner is wheeled in to Greg's room to shake the hand of the man who saved his life. Unfortunately, moments later Greg hears the screams of a mother in misery -- it's Demitrius's mom. Her son is dead.
Back at the lab, Nick, Warrick and Sara pack up for the night, deciding to head over and see Greg. Catherine tells them that except for Pig, aka Cole Tritt, none of the other killers are adults. They are teenagers committing murder because they had nothing better to do, and they don't have a conscience. While Nick sees the Vegas lifestyle as the culprit, Sara puts the blame on the kids. Grissom believes the current culture of shamelessness is at least part of the problem. And besides, "A moral compass can only point you in the right direction. It can't make you go there."