Grissom, newly appointed head of the crime lab, investigates the supposed suicide of a jackpot-winner. Meanwhile, Warrick has to deal with the fact that the shooting of rookie CSI Holly Gribbs was due to his failure to supervise her.

A kidnapping case becomes unusually personal to the usually detached Grissom. The 4-month old baby, Zach Anderson, was allegedly kidnapped from his home. A ransom note, found by his mother, is left in his crib. Many things seem strange about this case as more evidence are analyzed. When Zach's body is found on a nearby golf course, the team is sure that his death is no mere accident.

There's a serial killer on the loose in Las Vegas. Since this is a very high-profile case, the sheriff brings in the FBI to help. This annoys Grissom very much as the FBIs like to assume many things while he prefers to let the evidence speak for itself. Due to his refusal to cooperate, he is taken off the case. Grissom's team, however, knows better and keeps their boss informed on the details.

The detectives hunt for clues relating to a missing college freshman. Their hope of finding her alive diminishes as all of their leads on her turn cold.

A woman is found dead at a spa while a young man is found burying dead bodies.

Hollywood sex symbol Tom Haviland admits having had sex with a girl who is found in the same casino hotel, throat fatally pierced with a corkscrew. As he failed to clean up, the team quickly gathers enough evidence for a murder charge. His top lawyer chooses to demand a near-instant trial, leaving CSI almost no time to work out the part of Tom's buddy and a second victim, actually the first murder. Meanwhile Grissom's mentor and predecessor, Dr. Phillip Gerard, uses all his forensic expertise to question every move they make and discredit team members.

While performing on the stage, the comedian Dougie Max dies. Grissom, Catherine and Capt. Brass investigate the case and Grissom and his team conclude that he was poisoned by the expensive bottled water Innoko. When a teenager dies in a convenience store, Warrick is assigned by Grissom to investigate the case, and soon he finds that the youngster had drunk Innoko water. Grissom finds that the bottles came from the same lot, and was not a tampering case. Meanwhile, Brass asks Nick to reopen the case of Shelley Stark, who died in an accident in a bathtub and Brass did not call any CSI investigator. He has just seen her husband with a hot woman driving a Ferrari and he is intrigued, since the man was inconsolable. Nick and Sara reopen the case and find new evidences.

Several couples are killed bloodily after a wild party night in the same luxury hotel with Cameron and Mandy Klinefeld, or rather one somehow forced to kill the spouse. Nick is pleased to bump into former college mate Kenny Richmond, who works there, until it seems buddy boy passed confidential information to the press, which could get Nick fired.

The discovery of a dead man in the wilderness in a fursuit leads to an investigation at the goings-on at a furry convention.

Julie Waters, a dancer, has been missing for 6 days. A suspect, Howard Delhomme, calls the police and turns himself in. He refuses to talk to anyone but Catherine. Sarah and Nick want to work on this case because they see it as a career-making step. Grissom, to their anger and disappointment, hands the rein over to Catherine. Despite their initial antagonism, they all worked together to find the young girl.

When April Perez reports that her thirteen-year-old Alicia Perez has been kidnapped by an Afro-American man driving an old Buick, the CSI team investigate the scene and an Amber Alert is issued. Capt. Brass interviews the parents Sybil and Carlos and he learns that April had drug problem. Meanwhile, Grissom and Sara look through Alicia's room and Sara learns from Alicia's brother Daniel that his sister was in love with her schoolmate Jimmy Jones. When they meet Jimmy, the boy tells them that Alicia was upset since she would have to donate her kidney to Daniel and she liked to play soccer. When they find the body of Alicia dumped on the road, they make news discoveries about the case.

The CSI team is called to help when Karen Mathews reports her son, Jesse, missing from a playground where he was playing on the swings. Witnesses report seeing a man with a blue baseball cap near the swings. Clues in the park bathroom include blood and the boy's underpants. The boy is eventually found in a store, accompanied by a woman with a man fitting the earlier description. But the couple with the boy claim that he is their son Adam, while Karen insists he is her missing son Jesse.

A man walks into a shabby apartment and shoots the occupant. On his way home, a teenager's car crashes into his car. Ally Sullivan insists on calling the police but the man refuses. As he leaves, he sees her texting her phone. Thinking that she's calling the police, he kills her. The CSIs have a hard time finding this killer as he knows how to cover his tracks really well. He is truly a professional.

A criminal defense lawyer is murdered at her son's wedding and tied to the back of a car with beer cans. It is later revealed that she had a bad attitude at the bride, the groom's father, and basically everyone else.

A pedophile arsonist maintains his innocence in the disappearance of two young boys, but he is also willing to help the investigation by giving Grissom insight on the potential kidnapper's mindset.

CSI investigates the death of a toddler who was left in a cardboard box in a parking lot. A registered sex offender who is wrongly accused threatens Catherine after the real cause of death is identified.

A woman's unlikely suicide is tied to a bank robbery and a hypnotist, the team investigates the murder of a guidance counselor who was also a degenerate gambler, and Sara helps out in an euthanasia case.

CSI needs the help of an 8-year-old, HIV-positive boy to figure out who shot and killed his uncle and his mother during a street party in Koreatown.

The lab tries to unravel a complicated case involving fake FBI agents, an ultimate fighter, and a possible human trafficking ring.

Nick and Riley investigate the case of a badly injured skydiver, while Dr. Langston investigates the death of a religious leader out in the desert.

Langston investigates a homicide which is connected to the discovery of rare valuable chips from a legendary casino from the 1980s.

A young Hollywood actress is killed in what appears to be a simple drunk driving collision, but the team soon suspects that there is more to the case than meets the eye, and a shootout in the crime lab may confirm their suspicions.

The team discovers that a man who shot and killed a married couple is actually a victim of "Dr. Jekyll," and Dr. Langston could be the doctor's next target.

When two people who were thought to be dead come back to life, the evidence leads CSI back to a discredited ex-professor who conducted bizarre death-related experiments in the 1970s.

Sara suspects CSI is dealing with Armenian terrorists when she discovers a bomb on a man found in a flood channel, and Greg is accused of planting evidence in an old case.

A teenage boy shoots up LVPD headquarters and then holds Russell and one of his shooting victims hostage.

CDC may be dealing with a potential deadly virus outbreak in Las Vegas, and Sara and Greg may have been exposed to the virus while investigating a crime scene.