A woman found murdered in her home. Her resemblance to Sara causes Grissom to take a personal interest in the case and forces him to examine the decisions he has made in his life.

Grissom and Sara investigate the murder of a woman after a swap party. The married couples in the neighborhood meet and switch partners. With the help of a crime scene cleaner, Nick and Warrick find there was more to their crime scene than they first thought. Catherine wants a promotion to day shift supervisor.

Greg, for his final proficiency, has to determine how the Sherlock Holmes of a Sherlock Holmes club was killed. Nick and Warrick try to determine how the driver of jeep was killed when the car ran off the road. They have to do this under budget while Catherine is watched by Ecklie.

The CSI's are called out to investigate the disappearance of a boy whose father died four years ago. Soon a couple is arrested at a convenience store with a boy matching the description of the missing kid. The only problem is they both claim it is their son. Both parents have exactly the same picture of the boy, with a scar on exactly the same place on his face. They hope a DNA-test could confirm who the real parents are, but when this information comes to light, it lead to another bizarre twist, possibly murder.

The CSIs crash an elegant party for the city's crème of the crème to discover who killed a young man. The case gets a bit more personal for Catherine when her father, Sam Braun, is one of the suspects.

In the second part of this two-parter Grissom investigates the murder of an aging rockstar who is found dead in his kitchen with an exact replica of the crime scene on the counter next to him. Meanwhile, Catherine probes her own abduction and learns that someone may be targeting her family.

At Keppler's request Catherine uses a different approach to catch the killer, and in doing so she deceives the rest of the CSI team. The team soon discovers that something is amiss in Catherine’s investigation.

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

Grissom investigates the mysterious hanging death of a young man whose body looks like that of a female.

Two murders that happen during Las Vegas' annual bull riding rodeo are investigated by the CSIs, who find that the murders might be connected to illegal bull breeding.

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.

A popular young singer is found dead outside an infamous Las Vegas nightclub, leading the CSI team to uncover a link between that crime and a murder 50 years earlier.

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.

When a policeman kills another officer, the CSIs must look to the evidence to determine if the shooting was premeditated or an accident.

A legendary comic from the good old days of Las Vegas is set to reunite with his partner on stage for one night only, until one half of the famous duo is found dead.