Royce Harmon was murdered 3 months ago in a scene staged to look like a suicide. Now another murder has taken place. Whoever the killer is he has a thorough knowledge of forensics, he purposefully has left evidence, and has baffled Grissom and his team. Warrick and Nick investigate the case of a man who went over a cliff in his car and is now unconscious.

At a swanky fundraiser, attended by the sheriff, a woman turns up dead in the pool. The owner of the house is away and a young couple is housesitting. Warrick looks into an apparent professional hit in the glass elevator of one of the hotels.

Grissom and crew are called in after high roller Tony Braun, a known drug addict, is found dead in his house by a gardener. Since drug paraphernalia is discovered near his body and it is also determined that he had recently inhaled heroin, the cause of death is at first thought to be an overdose. But further examination of the corpse reveals that Braun had been restrained at some point with duct tape, leading Grissom to believe that the victim was forced to ingest lethal amounts of heroin and, perhaps, other drugs.

The CSIs come across an abandoned military compound being used by a small cult. The CSIs grow suspicious when they see that a mass suicide has taken place, but only 11 of the 12 beds are occupied.

The CSIs investigate the stabbing of a motocross racer who was about to leave town with a young woman he had been living with. Also, Nick comes closer to finding the truth about his kidnapping.

The investigation into a body found in a chimney leads the CSIs to re-open an investigation of an unsolved homicide of a female teenager named Caroline Fitzgibbons.

When a student is arrested and tried for the murder of a popular high-school girl, the suspect's 12-year-old sister confesses to the crime. This results in the judge giving the prosecution 72 hours to re-examine the evidence before the jury delivers its verdict.

The team investigates the death of a psychic who "saw" her own death while performing a reading for two other women. Greg reveals a family secret to Grissom but Grissom believes that science will be what solves the case.

A wealthy defense attorney is killed at her son’s wedding but Nick’s car, containing all the collected evidence is stolen and the case is compromised. After discovering new evidence, the team suspects that someone from the wedding party may be responsible for the murder.

In the season finale, the CSIs wait by the bedside of one of their own when he's shot in the line of duty. One CSI faces a hard choice by having the power of attorney over their injured friend and colleague. Meanwhile, the team also investigates the strange way of life of one man when he is found decapitated by a train.

Identical twins are found murdered on the same night. The CSI’s investigate the two separate murders only to find a twist in the investigation find that leads them in another new direction.

The terrified eyes and cryptic words of a murder victim haunt Sara while she processes the house where several showgirls were killed.

The CSI labrats take center stage to discuss the case of the Miniature Killer.

Several suspects in a murder case are UFO-club members who believe shape-shifting aliens have been working to conquer the human race for centuries

The CSI team investigates two unusual cases, one involving the suspicious death of a go-cart racer who took his hobby to the highway and paid the price with his life, and a murder at a hip new restaurant where patrons dine in the dark

The team investigates a girl whose whole family had been killed and she is supposedly possessed by the devil.

Sara questions her future as a CSI when a past case comes back to haunt her, the 12 year old Hannah, who has to back up her brother one more time with all new tricks up her sleeves.

Hodges stages hypothetical murders in the lab in order to give his fellow lab techs a chance to play CSI, but unbenownst to them he has other motives behind his actions. Meanwhile, after Sara's farewell, everyone tries to comfort Grissom.

The world of illegal dog fighting is explored by Grissom and the rest of the team when they take on the case of a wealthy socialite who was murdered. Meanwhile, Warrick struggles to clear his name in the recent exotic dancer murder case.

A deer is illegally killed, and the person found with the body in the back of his truck apparently dressed it in a tutu. The man, who was completely drunk when arrested, was being interrogated by Nick and Brass, and suddently tries to escape and is pepper sprayed. Unfazed by the spray, officers then taser him and he bursts into flames and dies. Meanwhile an unbalanced woman wearing a tinfoil outfit at the front desk tries to warn people (including Nick) of an alien invasion. After observing the burning man, she later turns up dead with green-tinted blood. When other people turn up with the same problem, it's up to the team to figure out why. Meanwhile, an old couple dies, apparently in their sleep... but there is evidence the cases are related.

After Warrick is shot in a Las Vegas alley, the CSI team comes together to deal with the aftermath.

A hypnotist bank robber becomes the prime suspect in a murder investigation.

After several victims are found dead while performing normal, everyday activities, the CSIs must find the reason as to why each of the victims remain upright after dying.

The team investigates the death of a woman who turns out to be the daughter of a wanted criminal.

When the team discovers a connection between a new murder and a serial killer, Grissom secretly joins the class of a criminal pathologist (Laurence Fishburne) to help crack the case.

The CSI team is shocked and saddened when, after working with Dr. Raymond Langston (Fishburne) on the "Dick & Jane" murders, Grissom announces that his time as a CSI has come to an end and offers Langston a permanent position on the CSI team.

Langston and Nick are called to investigate a murder at a fast food restaurant and have quite a task ahead of them when they discover that much of the evidence is coated in cooking oil.

The CSI are called to three different crime scenes in one night that are seemingly unrelated, but each case's forensic evidence reveals a common link

When the CSIs are called to a murder scene at a familiar motel, Nick is thrown for a loop as he pieces together three separate murder investigations that all took place at the same establishment over the course of a year.

When the producer of the reboot of a classic SF show is murdered at a Las Vegas science-fiction convention attended by both Hodges and Wendy (both, unknown to each other, fans of the original show), they find a connection with each other as the team investigates the crime.

A band of vicious bikers is given the go-ahead to take down one of their own when it's discovered that the guy is an undercover cop.

A cache of missing chips from a closed down casino turn up in Vegas and a string of murders follow, leading Langston to use deadly force for the first time in his career as a CSI.

After a beloved college football coach is found dead and his house drenched and spattered with his blood, the CSI team hunts for the killer who didn't find Coach Jimmy lovable at all.

When Hodges and Wendy take a group of high school CSI Explorer Scouts on a field trip, they embellish their role in solving cases and take their assignment a little bit too far.

The CSIs question the validity of an online picture depicting a murdered call girl until they find the same woman strangled to death in the dumpster that appears in the photo.

The investigators attend the gala grand opening of a mob museum, only to witness an attempted hit on mob lawyer and former mayor Oscar Goodman.

The team has few leads to go on when investigating a robbery-homicide at a themed wedding

When the CSI team is called in to investigate a man who is shot at point-blank range in a local casino, they shut down the entire building to find their killer.