一名妇女被发现在家中被谋杀。她与萨拉的相似之处使格里森对案件产生了个人兴趣，并迫使他审视自己一生中做出的决定。

格里森和萨拉在交换派对后调查一名妇女的谋杀案。附近的已婚夫妇见面并交换伴侣。在犯罪现场清洁工的帮助下，尼克和沃里克发现他们的犯罪现场比他们最初想象的要多。凯瑟琳希望晋升为白班主管。

格雷格为了最后的熟练程度，必须确定福尔摩斯俱乐部的福尔摩斯是如何被杀的。尼克和沃里克试图确定吉普车司机是如何在汽车驶离公路时被杀的。他们必须在预算内做到这一点，而凯瑟琳则被埃克利监视。

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.