Wealthy Roy Logan acts suspiciously when withdrawing $1,000,000 cash and his blood on his hands, but must be released for lack of a crime. When Catherine rushes after him with his spectacles, she gets a phone-call and is shown a severed finger proving Logan's adulterous lover Amanda Freeman was kidnapped. Logan ignores her advice, almost greedily handing over the ransom without proof of life, and Amanda is found where indicated- murdered days before.

Matt Phelps sends his two kids to bed, and out of the blue, there is a drive-by shooting and his daughter Aimee is shot and killed in her bed. Grissom, Warrick and Capt. Brass investigate the case and Grissom learns that Matt Phelps is Warrick's mentor and friend. Warrick's investigation is conducted based on his emotions instead of on the evidences with serious consequences for Matt and a suspect. Meanwhile, Nick and Sam Vega investigate the mysterious death of a boss of a four-men Internet service company in the air-conditioned servers' room. They find many secrets in the team but no suspect and no murder weapon. Until Nick observes the duct of the air-conditioning.

When Linley Parker survives a rape attack, the CSI team investigates the case. Linley identify her aggressor Dr. Todd Coombs, but their DNA do not match and Todd is released despite the identification. His brothers become the suspects based on the DNA results, but they do not find the guilty. When Linley is murdered, the CSI team discovers new genetic condition in the case.

When a group of fraternity members find a spot covered by maggots, Grissom investigates the scene and believes a student is providing the flesh to the maggots. Based on the uniform size of the bones and woods, Nick and Grissom believe a mulching machine was used to discard the body, and soon they find evidence in the machine. Based on a fingernail found in a garbage bag, Catherine concludes that the Blue Painter Killer is back. Now the entire team is working on the case.

While in a dinner party to celebrate the retirement of Director of Robert Cavallo and the promotion of Conrad Ecklie, Grissom is summoned by Capt. Brass to investigation a homicide in the Olympia Hotel. He stumbles upon Ecklie's right hand Sofia Curtis in the elevator and they go with Brass to the suite where they see the body of the teenage Nicole Jensen next to vomit. Soon they learn that the suite was reserved by the hotel's owner Charlie Macklin for his daughter Janelle. The McKinley High School is giving a homecoming party in the ballroom, but Janelle is giving a private party in the suite. Catherine, Nick and Warrick join the investigation and interview the guests. They note that Janelle is missing and they learn that two masked kidnappers have abducted Janelle. When Catherien and Sheriff Atwater interview Charlie, he tells them that he knows his daughter and that was a prank to get his attention. The CSI team proceeds the investigation and find the truth of what happened during the night.

After a massive shootout between the LVPD and a Latin American mob gang, the CSI team have to find and process hundreds of bullets to determine exactly what happened.