In part one of this two-part seventh season opener Grissom and Catherine handle the case of a women's dead body found at Cirque du Soleil by a performer. Meanwhile, an investor at one of Sam Braun's new casinos is shot to death during a party on the rooftop. Catherine's life is in jeopardy after visiting a nightclub with Nick. Grissom finds a miniature replica of a crime scene that he is investigating.
In the second part of this two-parter Grissom investigates the murder of an aging rockstar who is found dead in his kitchen with an exact replica of the crime scene on the counter next to him. Meanwhile, Catherine probes her own abduction and learns that someone may be targeting her family.
Coming straight from the perspectives of five people: Donna, Rebecca, Jack, Lou and Ray. All with one thing in common. They’re all dead. Brass and Catherine get to handle the case of Donna, who’s a cop from San Francisco, moonlighting as a bodyguard. Warrick and Greg work the case of Rebecca, who’s a former supermodel who died while hiking with her new husband Gavin. Nick and Sofia handle the case of Jack, a returning veteran from Iraq, who was killed in front of his wife and baby daughter who he just met for the first time. Grissom and Sara take the case of Lou and Ray whose bodies were found in Lou’s garage.
Three tourists are beat up, badly. One is dead, Alfonzo. Jessica is badly beaten but is still alive. Stanley, the last tourist is saved by Greg who ends up severely hurt in turn and ends up hospitalized after having to make a life altering decision.
Grissom and Sara may be secret lovers, but they still find ways to surprise each other like when their religious beliefs surface when two nuns find a body of a woman crucified on a makeshift cross. The woman was found in a church where the priest may be a man of sin instead of a man of God.
Grissom attempts to get a confession from a neighborhood pedophile by having him help in locating two missing boys. The sex offender is the main suspect. The investigation is more complex than the team ever thought it would be.
While investigating an elderly woman's murder, Grissom receives a miniature crime scene replica; Greg attends a hearing to ascertain his culpability in a teenager's accidental death.
Identical twins are found murdered on the same night. The CSI’s investigate the two separate murders only to find a twist in the investigation find that leads them in another new direction.
The Cadillac of an infamous 1970’s mob boss turns up in a lake, even though he disappeared years ago. A photo of current murder victims also turns up in the car, so the team must determine whether this current murder spree is related to the missing gangster.
Grissom investigates when a worker at a poultry processing plant is found dead in a stun bath used to electrocute chickens before they are slaughtered. Nearby, a miniature replica of the crime scene is discovered. It's eerily similar to two other replicas left at scenes of homicides. Also, a man and a dead woman are found stuck in cement at a construction site; and an elderly Russian woman is discovered dead in her apartment with her head in a gas stove, but Warrick thinks she was murdered.
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. Grissom prepares to leave on a four-week sabbatical.
The team has a hard time trying to understand Michael who has become a team member since Grissom’s teaching hiatus. They investigate the murder of an unidentified girl who may have been killed by a serial killer who has been killing since the early 1970’s.
At Keppler's request Catherine uses a different approach to catch the killer, and in doing so she deceives the rest of the CSI team. The team soon discovers that something is amiss in Catherine’s investigation.
Nick and Keppler investigate the bizarre world of the black market sales of body parts after they find a body that has been burned and the organs removed. The rest of the CSI team investigates the death of rich woman who was killed in her own home.
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.
Once he unseals a package sent to him through the mail, Grissom is floored when he finds a miniature crime scene inside. The finding is entirely more perplexing since the successive killer accountable for earlier related miniature crimes is now deceased. Grissom plows to examine the miniature and discover the actual location, when the investigation makes it clear the murder showed has yet to happen, but is probably going to happen soon.
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.
After a man is killed in his limousine, Greg finds that the murder victim has ties to the man he had to kill in self-defense. The team finds that the brother is involved in this investigation and has to deal with him and his hostile mother.
Grissom investigates when a sadistic client tries to murder Lady Heather (Melinda Clarke), who makes the probe more difficult when she refuses to name her attacker. Also, Grissom's reunion with Lady Heather makes Sara uneasy.
As the CSI's continue their search for and discover the identity of the "Miniature Killer", Grissom and Sara's relationship gets exposed to the rest of the team as she goes missing during the investigation. The "Miniature Killer" is finally captured, but not before a member of CSI becomes the killer's final victim.
