A wild night in Las Vegas has the CSIs simultaneously investigating four fatalities. Greg Sanders' first day in the field has him assisting Grissom's investigation of a fatal nightclub shooting. Meanwhile, Catherine probes into the death of a stripper found dead in a hotel room, while Sara and Nick look into the strange case of an "alien" body found near Area 51.

Heavy rains in Vegas wash up a body in the storm drains. As the team investigates, they find bones from another murder.

A child is abducted. As the Amber Alert goes out, the entire team investigates in a race against time. Lindsay Willows is found hitchhiking, to the alarm of Catherine.

A woman is found dead in a hotel suite with symptoms of the ebola virus. Another woman is found dead with similar symptoms. Catherine and Nick investigate. Sara and Greg, helped by Grissom, try to determine how a the owner of a home was killed. His home was tented for infestation.

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.

The killer from The Execution of Catherine Willows returns with deadly results. The entire team is engaged in a race against time to stop this sadistic killer from succeeding again. Grissom is additionally distraught by the idea that this killer is smarter than he is.

Grissom is called to a murder of a 17-year-old in a casino penthouse. Sophia Curtis (Louise Lombard) joins him in his research, she normally works in the day-shift. The entire team gets involved when its discovered that a kidnapping took place along with the murder.

A woman who was pulled over by police is found murdered two miles up the road from the stop. It's not long before Robbins determines that the woman is, genetically speaking, not a woman.

Grissom is confronted with new evidence while on the stand of a murder trial of a restaurant owner. This development requires the reopening of the case and Eckley initiates an inquiry into Grissom and his team. The results of the inquiry lead to dramatic changes of the CSI team and the series.

Grissom and his team investigate the starving death of a five year old boy. They discover the boy has siblings who are in danger too. Catherine and her team determine who killed a prisoner in a holding cell brawl.

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 a jeep was killed when the car ran off the road. They have to do this under budget while Catherine is watched by Ecklie.

The swing shift has a busy time. Warrick looks into the murder of man by someone who apparently needs a wheelchair. Nick looks into the murder of woman in the subculture of the narcocorrido, songs about drug murders. The night shift is slow and lends help to Catherine's team.

Catherine, Warrick and Nick find the body of two women at a construction site buried under tar.The swing swift are brought into the world of foreign "mail-order" brides. Sara and Catherine have a dispute in which Sara gets suspended by Ecklie for acting insubordinate toward Catherine and himself. Sara opens up to Grissom about her childhood past.

Grissom, Sofia, Sara and Greg investigate the disappearance of a woman coming home from a night out with a friend, her abandoned car found on the edge of a highway. Catherine, Warrick and Nick investigate the deaths of a hunter and his prey, a Kodiak bear.

When a major Las Vegas player is found dead, Ecklie orders both teams to investigate the case. The man who had secrets on everyone in Vegas had a very big one of his own.

Catherine, Nick, and Warrick investigate a badly mutilated body in the woods. The cause of death was a shotgun blast. Nearby is a beaver dam made in part with cash. Grissom, Sarah, and Nick try to determine how a man was killed in a hotel room. It leads them to a convention of big women.

A serial killer strikes again, and the CSI team tries new technology using evidence from a prior killing. They find a fingerprint belonging to Jesse Acheson, who becomes the prime suspect. A boy confesses to the killing of his brother, but evidence suggests that he may not have committed the crime.

Grissom, Sara and Nick investigate a wildfire that killed one man and badly burned a woman. Catherine, Nick and Warrick get the case of a family of three murdered in their home.

One night, four cases. Grissom and Brass get a stolen hummer and a taco stand. Warrick gets a dead car show girl. Sara and Greg get a dead bodybuilder. Nick gets a dead boy found on a bench.

Brass travels to Hollywood, California to try to track down his estranged daughter's friend, meanwhile trying to rekindle some kind of relationship with her.

Grissom and Sara investigate the murder of a mental-hospital patient and quickly narrow down the suspects to a handful of other patients and staff members.

A man (Alan Rosenberg) whom Catherine flirted with at a bar reappears in her life as a suspect in a murder investigation.

Two amorous freshmen are found dead on a sleeping bag in a dorm room, and Sara and Greg run into one dead end after another as they try to determine why the students were killed. Warrick, Nick and Catherine figure out how a man is found dead in the center of a crop circle. Ecklie is called into duty for a man found dead in his car and his body later goes missing.

The CSI teams come together to save one of their own when they learn one team member has been kidnapped and buried alive, and now they must find him before he suffocates under five feet of dirt.