Delko is still out on leave so Jesse Cardoza (a former Miami detective who has spent the last twelve years working in L.A.) is brought back on the team. He's at the lab waiting to talk to Caine, and he surrenders his weapon and says he'll wait. But a man in a helmet forces his way into the reception area. He has a shotgun, and he tosses out a few flash grenades, which disable the police officers and others at the lab. Then he takes five hostages, including Cardoza. The gunman also wants to get in touch with Horatio Caine.
Caine arrives, and the rest of the team work on getting the video feed from inside the lab. The gunman calls and introduces himself as Ted, and Ted confesses that he wants Caine to make sure justice is done. Meanwhile Calleigh and Ryan go over camera footage of the parking lot, which reveals which car is Ted's. Footage also reveals that Cardoza gave up his weapon at the front desk, so he's not in league with the gunman either.
Cardoza hides his badge to prevent himself from being ID'd as a cop. When the hostages have to give up their wallets and purses to Ted, Ted notices that Cardoza has a California driver's licence. Cardoza says that his car was stolen so he's at the station to file a report. Ted threatens to kill the receptionist if he finds out that Cardoza is lying.
The team examines Ted's van and discovers that he has blueprints of the lab, and that he's also on antidepressants. The empty medicine bottle also gives the team Ted's true identity. Meanwhile in the lab, the A/C has been cut off, which is starting to make Ted uncomfortable. Frustrated, he fires a round into the air, which catches Caine's attention. Caine calls and asks if there's anyone hurt, and he also tells Ted that they know his real name. Should they contact anyone? Ted says to find a woman named Tonya. The A/C turns back on, and Ted, paranoid that there might be cops in the airvents, ends up shooting the receptionist in the leg.
Cardoza starts to tend to the receptionist's wound, and the receptionist asks him if he's sure about wanting to work here. Ted overhears and realizes that Cardoza must be a cop. Crane enters the lab, and Ted gives him his demands. Caine says he isn't there to negotiate and leaves with the wounded receptionist.
Calleigh and Ryan go to a location Ted shared: a check-cashing store, where they demand that the owner give up $100,000. The money is returned to the lab, and Ted (real name Matthew Sloan) requests that he be given a way out. Later, a helmetted gunman walks out of the building with the two remaining hostages. The snipers are about ready to take the shot but Caine recognizes sees something weird about the man's shoes. The gunman is actually Cardoza, with tape covering his mouth and his hands taped to the shotgun.
Caine checks the cash and discovers it's counterfeit. Sloan wanted them to find out about the money. The owner of the check-cashing store, Ripley, is brought in for questioning. Ripley has evidence of chemical burns on his hands, which might mean that he was using something to strip the ink off of the bills and then reprinted them into whatever denomination he wanted. Ripley and Sloan went into a business deal together, but the business went bust. Ripley wasn't as hard up on cash afterwards as Sloan was, and it was because he used counterfeit money on his end of the deal.
Calleigh and Rick go talk to Tonya, who turns out to be Sloan's ex-wife. She tried to convince her husband not to go through with the deal with Ripley, but he didn't listen, and they lost all their savings because of it. By court order, Sloan could only get visitation rights with his son if he was taking his meds. Cane tells Sloan that Ripley's going to prison for his crimes, but Sloan says that there's another person who also ruined his life. Tonya filed for sole custody of their son, Jason. Jason was in a cast, his injury apparently caused by Sloan. There's evidence that the door at Tonya's house was knocked down, and Calleigh finds a hair by the window. The hair belongs to Tonya's current husband, not to Sloan. It's suggested that the husband broke down the door to make it look like Sloan wasn't fit to even have visitation rights.
Calleigh tells Cardoza that they have to find evidence to clear Sloan's name. Jason got the cast after Sloan lost custody, which meant that Sloan couldn't have done it. The bruises were made by a small hand, so it turns out that Tonya might have been abusing Jason. Jason says that his dad never hurt him and Tonya is brought into the station.
Away from the lab and at a bar, Sloan watches as the news talks about Tonya's case, and he's suddenly taken into custody. Before he's taken away, however, Sloan gets to talk to his son. Later, the team are together to welcome Cardoza to CSI, and Cardoza has to pay for the drinks. He asks Caine what he wants, and Caine orders a club soda, since he's the designated driver.