A Cirque du Soleil dancer is killed during a show which sends the CSI crew backstage to investigate her murder. Meanwhile, after Catherine and Nick go to a club to watch a performance by John Mayer, Catherine has to rely on her CSI skills to uncover who is targeting her family. Elsewhere, Grissom is puzzled when he receives a mini-replica of a crime scene he is investigating.

Grissom’s fascination continues with a miniature replica of the crime scene he’s investigating where a rock star was murdered. With the clues that the replica provides, Grissom works to find the killer. Meanwhile, Catherine finds herself in danger and continues to hunt for the person responsible.

Donna, Rebecca, Jack, Lou and Ray all share a similar characteristic -- they’re all dead. The team splits up to solve their murders: Brass and Catherine pair up to take on Donna’s case, a former cop who was working as a bodyguard; Nick and Greg investigate Jack’s death, who was an Iraq veteran that was killed in front of his wife and daughter; Warrick and Sofia take on the case of Rebecca, a former supermodel who died while hiking; and Grissom and Sara pair up to look into the deaths of Lou and Ray whose bodies were found together in Lou’s garage.

An innocent man is attacked and beaten to death by a man in a black cape. When the CSIs investigate, they find that a similar incident took place only moments earlier. The incidents continue to occur and the crew follow the trail of evidence hoping to get to the next victim before it's too late. But when Greg interrupts a beating in progress, he is forced to make a decision that will change his life forever.

The CSIs investigate the death of Charlotte Sommerville who was found crucified in a church. The case takes a twist when the CSIs uncover that Charlotte was having an affair with the church’s priest and a car dealer that Charlotte knew in high school.

Two young boys go missing and Grissom must get into the mind of a local sex offender who emerges as the primary suspect. In order to find out who the real abductor is, Grissom is forced to ask the local pediphile for help. However, the task of finding the culprit becomes more complicated than Grissom and the rest of the CSI crew ever expected.

The CSI team investigates the death of a retired cocktail waitress with serious cancer. Did her recovering junkie nephew or her drug dealing neighbor murder her for her pain medicine? That's the working theory until the nephew finds a miniature crime scene on his aunt's porch - an exact duplicate of the crime scene and similar to a diorama they received earlier. Elsewhere, a coroner's inquest is called to examine Greg's conduct in the events that led to the death of Demetrius James and Greg receives an unpleasant surprise at the end of the episode.

Identical twins are both found murdered on the same night, leading the CSIs to investigate whether or not the two murders have a connection.

The remains of Mickey Dunn, a wanted Las Vegas mobster who disappeared in the mid 1970s, are fished out of Lake Mead with a bullet hole in the head. Soon afterwards, a wheelchair-bound man is murdered and a photo found on his body shows the victim with Dunn and three other men. Dunn and the victim have Xs on their faces. It quickly becomes apparent that the other three men may also be targets.

Grissom is called to the scene when a poultry processing plant employee is found dead in an electric stun bath that is used to electrocute chickens. The team is shocked to discover a mini-replica of the crime scene, a calling-card similar to the replicas found at two other homocides. Meanwhile, the team looks in to the death of a man and an woman who were found stuck in cement at a construction site as well as the death of an elderly Russian woman.

Catherine testifies in a murder trial in which a man is accused of murdering his own mother three years ago, but the suspect is found not guilty. Catherine, however, believes he did commit the crime and that he may also have killed two other people, so she sets out to find the other victims. Catherine's probe leads to a small Nevada town where an elderly woman and her daughter were fatally stabbed and shot three years earlier. Back at the lab, Grissom prepares to leave on a four-week sabbatical.

As Catherine and Keppler begin to investigate the murder of a teen-aged "Jane Doe," both agree that the killer, who was meticulous in removing evidence from the body and its surrounding area, is likely a repeat offender. Soon they and the rest of the CSI team uncover three similar unsolved cases that suggest the serial killer has been active since 1975.

Keppler persuades Catherine to help him fake a crime scene and deceive their colleagues in a controversial plan to catch the west coast's biggest illegal drug supplier, who is the leading suspect in the murder of an anti-drug assemblyman who was gunned down in the desert. Keppler concocts the plan when the suspect disappears and his trail grows cold after several weeks.

Nick and Keppler are sent deep into the bizarre world of the black market body parts sales after a body is found burned with its organs removed. Meanwhile, the other CSIs look into the the death of a wealthy woman killed in her home.

In this interlude.. Grissom returns from his sabbatical; Keppler is put into a compromising position when the bodies of a Trenton police officer and a hooker are found in a hotel room. The man who found them is a retired New Jersey cop and close friend to Keppler, who doesn't reveal their relationship.

The miniature killer sends a message to Grissom -- another miniature that foreshadows the death of a woman and her cat. With less than 24 hours to prevent the murder, the CSIs work quickly while Grissom regrets holding up the investigation by going on sabbatical.

Grissom and his team are discouraged when they find a pool of blood as they begin investigating the disappearance of a high school basketball star and his cheerleader girlfriend.Grissom’s quip that the young lovers may have run off to Mexico is soon quashed by the discovery of drops of blood by Ryan’s vacant parking spot at the school. After finding a letterman jacket and cheerleading sweater in the field house and a pool of Ryan’s blood nearby, the team tries to determine what went awry.

While processing a murder scene, Sara is haunted by the last words and eyes of the sixth victim.

A high profile man is murdered in his limo and after investigation, Greg learns that the victim had connections to a man he killed in self-defense. The CSIs uncover that the brother of the man killed in self-defense may be behind the limo murder.

When Grissom and the team head out on cases, Hodges, Archie, Henry, Mandy and Wendy team up to try to solve the miniature killer cases.

The CSIs must determine which of several life-threatening actions against a washed-up boxer lead to his death.

The CSIs investigate the murder of a woman who is a part of a UFO club that believes aliens have mated with humans for several generations in order to conquer the world.

Grissom is reunited with Lady Heather during an investigation, much to Sara's chagrin.

The team gets closer and closer to identifying the miniature killer, but when Sara goes missing, Grissom must expose their relationship to the team in order to save her life.