Gil Grissom is the supervisor of the graveyard shift of Las Vegas' elite crime scene investigators. Holly Gribbs, fresh out of the academy, joins the team. Jim Brass is head of the unit and is trying to scare Gribbs from CSI. Catherine Willows, mother of a young daughter, is the number two CSI on this shift. Warrick Brown and Nick Stokes are competing to solve their 100th case to earn a promotion to CSI 3. Grissom investigates a murder staged to look like a suicide with precious little evidence. Warrick and Catherine take the case of a drunk who breaks into the house where he had been staying and is shot to death. Nick talks to a man who picked up a woman who drugged and robbed him.

When a teenager and her sister are the sole survivors of the gruesome murder of four members of one family in a quiet suburban neighborhood, Grissom and his entire team investigate the crime. What initially looks like a bizarre cult murder becomes more disturbing when they discover the motive behind the massacre.

A man convicted of arson and the murder of his wife and child seeks assistance from Grissom to help prove his innocence. Meanwhile, Catherine and Nick investigate the underground world of sports gambling when a teenager is murdered at close range.

A bomb goes off in an office building killing one and injuring many more. The chief suspect is a security guard who left minutes before the explosion and has knowledge in bomb making. Nick helps his prostitute friend again. After giving in to his passion, she is found dead the next morning. Naturally, Nick is a suspect and to make it worse, Ecklie has the case.

When a single human bone is discovered in the desert, Grissom and Catherine must cover miles of territory to find the rest of the skeleton. And Warrick and Sarah trace the death of a male stripper to members of a wedding party who may have celebrated a little too hard the night before the nuptials.

A body is found in a pottery store in what's apparently a robbery that was interrupted. Fingerprints at the scene seem to match a twenty year old kidnapping case. Sara and Warrick look into a case where a woman burned to death in her home. The woman was burned to an ash but only the chair she was in was burned, the rest of the house is fine. Sara believes they have a case of spontaneous combustion.

A couple leaving a restaurant on their anniversary are killed in the street and their car is stolen. The crime scene is compromised when it rains shortly after the CSIs arrive. It gets more mysterious when the car is found and it becomes a new crime scene. Catherine looks into the collapse of a city owned residence that kills three elderly women. She runs into problems with the city engineer responsible for the building.

Two women run over a deaf man but they didn't kill him- he was already dead. Grissom has to find out who did it and he's not getting help from the deaf man's school. Catherine and Nick investigate an apparent mob hit that leaves five dead in a coffee shop.

Grissom, Nick, and Warrick take the case of a jogger who was killed by a wild animal in the park. It gets complicated when they discover that the jogger had his liver removed after he was killed. Catherine and Sara investigate the death of a six year old girl at shady carnival.

On the day Grissom has to evaluate his team, a head is found in the trunk of a car. While Gil and Catherine work on the head, Sara and Nick investigate a body in the desert that's missing it's head. Warrick looks into a murder in juvenile detention in which his young friend James is the only witness.

The team is investigating the ongoing murders by a signature killer. The killer has some knowledge of forensics and has left little evidence behind. With the investigation somewhat stalled, the sheriff invites the FBI to join the case. This makes Grissom angry and it only gets worse when Sara offers to bait the killer.

Grissom investigates a possible suicide at a high-profile construction site. Catherine takes on a case with a teenage boy who dies while in session with his female psychologist,

When the class clown at the local high school is found murdered, the CSI team is called to investigate, while Nick and Sara respond to the crime scene of a decomposed body found in a bag.

Grissom, Sara and Warrick are called on to investigate an abandoned, blood-splattered apartment and Nick and Catherine must examine a dead scuba diver lodged in a tree.

Grissom and his team investigate a murder suspect who is caught red-handed -- burying the victims -- while Catherine and Warrick take on the case of a woman found dead in a hotel spa.

Grissom and Nick investigate the death of a book restorer while Catherine and Sara are called to the scene of a fatal train crash.

Grissom investigates the murders of four monks who were shot point blank while chanting in a Buddhist temple; Catherine reopens a cold case in which her best friend was murdered, after the man convicted of the crime claims he's innocent shortly before he dies.

Grissom and Catherine investigate the stabbing death of an 80-year-old woman who lived in a run-down house full of cats; Nick and Sara comb through the remains of a car bombing that was, apparently, a murder plot gone awry.

Fifteen years ago, Catherine helped put John Mathers on death row for the rape and murder of a coed at a nearby college. Her body was dumped in a trash bag, and two other girls found the same way were also linked to the suspect. As the episode opens, Mathers is about to be executed when he's granted a stay based on new DNA evidence. But while Catherine awaits the results of tests on hair samples found on the first victim, another girl at the same school is murdered... and discarded just like the first three - meaning the wrong man could be behind bars.

A middleweight boxing champ dies in the ring after taking a brutal beating from his nemesis, but Grissom finds evidence that points to murder. Outside, in a nearby parking lot, Catherine works a crime scene where a Los Angeles gang member was gunned down, apparently by a rival gang. Also, Nick investigates a jewelry-store robbery.

Grissom, Warrick, and Nick investigate the case of man who apparently was murdered and pushed off a six story building. Grissom's involvement is cut short by renewed hearing problems. Catherine looks into the murder of man outside of his regular bar.

Grissom and Catherine investigate a movie-goer who was stabbed to death; the team comes to a forensic impasse while processing a teenager who died from a gunshot wound.

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.