Tony Braun, a drug addict and high roller, is found dead in his house. Grissom and his team are called in, and judging by the drug paraphernalia surrounding the body, they assume the cause of death is an overdose. However, further investigation leads them to believe that the victim was forced to ingest lethal amounts of a combination of heroin and other drugs.

The CSIs are sent to investigate when a young college student vanishes, seemingly off the face of the earth. They are able to uncover some evidence, but each suspect only leads the crew to more dead ends. The CSIs are lead to believe that the Chaos Theory - seemingly-innocuous events can have a deadly outcome - may be the reason for her mysterious disappearance.

Grissom investigates what seems to be a suicide at a construction site. Grissom is lead to believe that the man was murdered, and uses theories on electrocution to find the killer. Meanwhile, Nick and Catherine take a case with little evidence. A young boy died during a session with his psychologist, and when angora fibers are found on his underwear, Catherine and Nick believe that the psychologist was using an unusual type of therapy that turned deadly.

After the class clown at a local Las Vegas high school is found dead, the CSIs are called to investigate. They uncover that the class clown was more of a class bully, leading Grissom to believe that a fellow student is to blame. Meanwhile, Nick and Sara investigate when a badly decomposed body is found in a bag.

Grissom, with help of Sara and Warrick, investigate an apartment found with blood spattered on several surfaces. They become suspicious when the latest tenant of the apartment claims that his girlfriend, who was reported missing, was visiting her parents, but the parents claim she never arrived. Meanwhile, Catherine and Nick are sent to the scene when a dead scuba diver is found lodged in a tree near Lake Mead. Did the diver fall victim to a murderer or an Urban Legend?

Grissom, Nick, and Sara investigate what seems to be an open and shut case when a murder suspect is caught burying the victims. However, the case takes a turn when Grissom uncovers that the suspect is the brother of a known criminal, leading him to question the evidence. Meanwhile, Catherine and Warrick investigate when a woman is found dead at a hotel spa. They must determine if she died due to the heat or if foul play may have been involved in her death.

Grissom and Nick take the case of a book restorer found dead while Sara and Catherine investigate a fatal train crash. The book restorer is found dead and locked inside a cage, leaving Grissom and Nick to determine if the restorer killed herself or if her death was a homicide. The evidence leads them to an autistic co-worker who may hold the key to solving the crime. Meanwhile, Catherine and Sara sort through the wreckage of a train-SUV collision to determine if the crash was caused by road rage or a careless accident.

Grissom and Catherine investigate the death of a woman whose body is found in a sandbox. Her violent death leads them into the world of SandM clubs. Meanwhile, Warrick and Sara investigate a shooting that appears to have happened during a robbery, but are things as they seem?

Grissom, Nick, and Warrick investigate a casino heist in which several innocent bystanders where shot, while Catherine and Sara investigate a murder in the desert. When the evidence from both crime scenes are compaired, the CSIs are led to believe that there is a connection between the seemingly different crimes.

While Grissom is away, Warrick is put in charge. He and Sara take the case when a con artist, who was involved with Brass's daughter, is murder. The evidence leads the team on a counterfeit investigation. The CSI's number one suspect is Brass's daughter, forcing Captain Brass to take himself off of the case, but he has a hard time doing so.

When a well-known real estate entrepreneur is found dead in an elevator, the CSIs are called to investigate his murder. Their job is made more difficult when the team realizes that the crime scene has been tampered with -- the victim has been redressed. The team soon discovers that the cause of death was poisoning and that the man's organs have already been removed and donated, making the crime even harder to solve.

Grissom and Sara investigate the double murder of two people found hidden in construction pipes. They find that the victims are sisters and have a common link: a former prison inmate. Meanwhile, Catherine and Nick investigate what was originally assumed to be a hunting accident, but further inspection of the crime scene reveals that the death was no accident.

The team investigates the crime scene left by serial killer Paul Millander after his latest murder. Probing of the crime scene and the files from his past murders, the team finds that all the victims shared the same month of birth. Grissom begins to assume that he's the next target of Millander when the common birth month happens to be his as well.

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. .

As Grissom investigates the murder of a photographer whose remains were left at a body farm that is used for CSIs to study corpses, the team begins to question Grissom's leadership skills. Grissom and the team find that the man was shot to death, but there were no bullet fragments left in his body.

After a fight at a sporting event, a man ends up at the bottom of a pile. When the fight ends and the pile breaks up, the man is found dead with a gash across his neck. Grissom, Catherine and Sara are called to the scene to determine whether the death was an accident or if foul play was involved. Meanwhile, Warrick and Nick investigate the seemingly drug-related death of a sax player at a casino.

Grissom is called to investigate the murders of four monks who were shot while chanting in a temple. Meanwhile, Catherine reopens a case involving the murder of her best friend when the man convicted of her murder confesses right before his death that he wasn't the murderer.

When a bus carrying 23 passengers crashes, killing nine people, the driver of the bus tells the team that the steering went out and it was impossible for him to control the bus. After learning that a recent parolee was on the bus, but is unaccounted for after the accident, the CSIs begin to assume that foul play was involved in the accident.

Jane Galloway, a woman who lives a secluded life -- the shades are always drawn, doors are always triple-locked -- falls victim to a serial killer. The CSIs are called to investigate the scene and have to find out who killed Jane and how the killer could have gotten into the house with out tripping Jane's security system.

While Grissom and Catherine work together to solve the murder of an 80-year old victim who lived in a house full of cats, Nick and Sara investigate the scene of a car bombing that seems to be a murder plot gone wrong.

Grissom and Sara are called to the scene when a man's body that had been soaked in lye is found buried in a park. Meanwhile, Nick tries to determine how a man drowned in the desert.

wild party ensues at the home of Chief Duke Rittle. As the party continues, little Sasha Rittle looks out her window and sees several people. She looks at the clock. The time is 12:20. The scene fades to around 3:45 am, and Sasha bursts awake to hear two semi-automatic 9 MM rounds going off. The door slowly opens and a mid-30s man emerges from the shadow.

When a young woman is discovered stuffed in a shopping cart under a freeway, the CSIs are called to the scene to investigate. The find that the woman's body is disfigured and starting to decompose. Her face is covered with gashes and scars, leading the team to believe that someone shoved her face into a fan. After seeing the rest of the contents of the cart: an expensive handbag, fashion magazines and a leather day planner, Grissom is lead to believe that not only did someone want her dead, but they wanted her ugly.