Season 4

Two couples meet in a bar and one of the couples is murdered. When a second couple is murdered in a similar fashion the team suspects a pair of serial killers are on the loose. The case is complicated by leaks to the press and a judge reluctant to issue a warrant. Catherine gets some troubling news about her father's murder trial.

When the lead suspects in Grissom's serial killer case are murdered, Grissom suspects an inside job. Grissom and Brass are at odds when Grissom suggests it was a cop. Catherine and Sara investigate what happened to a college football fan when his bloated body is found in a bathtub.

Grissom and Warrick get the case of an old woman found mummified in her closet. Sarah and Nick arrive to investigate a breaking and entering to find a raped teen. These cases are not as disparate as they first seem. Catherine looks into a gun found by a boy. The gun is connected to a week old murder across town that Warrick caught.

During Vegas's latest Heat wave of triple digit temperatures, Gil and Catherine investigate a baby locked in a car. Warrick investigates a man dead of an apparent heat stroke in his house. Nick and Sarah investigate a woman's body found floating in the lake with a blow to the head.

The team is introduced to the ""Furry"" side of Vegas when a man is found dead on the side of the road, dressed in a racoon suit. Elsewhere in Vegas, a gunshot victim is found in a deep-freezer, frozen solid.

A severed head is shipped to Dr. Robbins from Jackpot, Nevada. Grissom goes to Jackpot to find the rest of the body and gets very little cooperation from the locals. Catherine gets an unexpected gift from her father.

Warrick's appearance at the preliminary hearing on a rape and murder case goes terribly wrong when the only piece of evidence is thrown out on a technicality. Grissom and the team have 24 hours to make the case with new evidence or the killer will go free.

A suspect's infatuation with Catherine results in her taking over a high profile case. The case is a missing woman who aspired to be a showgirl. Sara and Nick are angered since it takes the career making case away from them.

The sheriff is under political pressure to find who killed an air marshall with a car bomb that the sheriff witnessed. Grissom, Catherine and Nick are pressured to produce results. Warrick and Sarah try to find the murderer of the wife of a singer who headlines on the strip.

A teenager is found murdered on a construction site. Grissom, Sarah, and Warrick follow the lead of blood on a hammer. Nick, with an assist from Catherine, tries to find how a woman was killed by a gunshot on her lawn when no one nearby had a gun.

The lone holdout on a jury is found dead in the jury room. The eleven jurors who were voting guilty and who hated the dead juror are the natural suspects. Nick reopens a four year old case when the sister of the victim comes forward with new evidence.

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.

Three little CSIs (Grissom, Sara, and Nick)respond to an electrocution at a casino. The casino is hosting Japanese antiquities. The electroctution is just a ruse to steal the central piece of the exhibit. Catherine and Warrick deal with a vampire murder.

A robbery at a grocery store results in a shootout leaving five dead. The police officer at the scene believes Grissom has a grudge against him. The entire team has to process the enormous amount of evidence at the scene.

The whole team must investigate a crime where a husband and his porn star wife were murdered execution style. Things get personal for Catherine when Grissom talks to her about her evaluation. Brass believes that Sara may have some type of problem.

Catherine and Sara deal with the death of what at first seems to be a transvestite. Later during autopsy they find out that the make-up he seemed to be wearing was actually facepaint, he was a clown. Grissom, Nick, and Warrick deal with the death of a man in a homeless area. They found out he worked in a recovery center for drug users.

A mutilated female body is discovered tied to the undercarriage of a bus carrying prisoners from a women's correctional facility after a severed arm flies out from beneath the vehicle and strikes a car. Catherine leads the investigation and at first believes the woman was escaping, but the evidence increasingly points to murder. Back in town, Warrick probes the death of a gambler who was stabbed multiple times in his brother's kitchen.

A violent murder in a casino parking garage and another episode in the police interview room lead the CSIs to one shocking discovery after another. The case involves a missing woman, a long dead body and a missing child.

Warrick, Catherine, and Nick try to determine the cause of a house fire that kills a teenage kill. The fire is in the same neighborhood as a similar arson fire. Grissom and Sara investigate a man found dead with letter tiles in his stomach. The man was a competitor in a word game tournament.

Grissom, Catherine and Nick investigate the death of a runner during a competition. Meanwhile Sara and Warrick investigate the death of couple in a hotel room, initially thought to be a murder-suicide. Both cases take place during this 'cop' competition , with more than 20.000 attendants (all of them cops). This gives the investigations an interesting turn, as almost all the suspects and all dead people are cops.

A roller coaster runs off track leaving 6 people dead. The CSI team must uncover whether this was an accident, or foul play. Warrick and Catherine try to find the killer of a 13 year old girl.

Two men are found murdered after scamming Sam Braun's casinos. Grissom and Warrick investigate after Catherine is thrown off the case. One of the suspects is the son of a man Braun caught cheating. Nick gets the promotion that Sara coveted.

A casino employee is beaten and raped on her way home from work, but she survives and identifies her attacker. Unfortunately, a DNA test sets him free and Grissom must wrestle with whether evidence can ever lie. Later, Grissom comes to the rescue of a coworker who ends up on the other side of the law