Mac, Bonasera, Monroe, Flack e il nuovo interesse amoroso di Mac, Peyton Driscoll indagano sull'omicidio di un venticinquenne, avvenuto dopo una proposta di matrimonio. Contemporaneamente Messer, Hawkes e la nuova arrivata, Jessica Angell, indagano sull'omicidio di una giovane benestante.

Bonasera, Messer, Monroe, Flack e Hawkes indagano sulla rapina in gioielleria commessa da tre ragazze vestite come Audrey Hepburn in Colazione da Tiffany;Intanto Mac e Angell indagano sull'omicidio della moglie di un consigliere comunale, sospettando proprio del marito.

Durante la festa di una confraternita, una giovane ragazza viene ritrovata decapitata con indosso una maglietta raffigurante l'Idra a sette teste. Pochi giorni più tardi, troveranno il corpo di un buttafuori, senza occhi e con una maglietta raffigurante Argos, il guardiano di Zeus.

Messer, Monroe e Hawkes indagano sull'omicidio di una ragazza punk avvenuta in un vicolo vicino al locale dove si era appena esibita in uno spettacolo con il gruppo delle “Ragazze Suicidio”. Intanto Mac e Bonasera indagano sull'omicidio di un giocatore di basket, che era appena uscito dal tunnel della droga.

The CSIs are investigating the murder of a hotel concierge, but while doing this they hear gun shots fired across the street and find a woman clutching a gun over two dead bodies.

A young woman dies after she starts bleeding from the eyes, nose, and mouth while at a party aboard a subway train. Mac originally believes she is the victim of a biological attack. Later, it is revealed that Sheldon knew the victim. Across town, a wealthy playboy is found dead in an indoor lap pool in his penthouse suite. The investigation reveals that he was murdered and his last maid was fired two days earlier.

The next case for the CSI’s gets even tougher when a paintball player turns out to be the prime suspect and later goes missing the team also has another problem the evidence that should point to the prime suspect points to someone else.

The next case takes us back to Dr. Sheldon Hawks' past and the reasons he chose to change jobs in the medical profession. The CSI team may find it extremely difficult to find out who committed the murder of the 19-year-old woman who recently started recovering from an accident.

The team is led to a crime scene in the middle of the city involving a parachute jumper whose parachute apparently failed. And one CSI is injured when a snake is found at a crime scene.

After a bartender is murdered The CSI team must prove that Hawkes did not commit the murder. That only becomes more difficult when the team is pulled off the investigation.

The CSI team has a problem after learning the family is deaf: now they have to find a new way to catch the killer. Meanwhile, more information is given on Lindsey's horrifying past and what led her to become a CSI.

The team must find out if one team’s fun led to murder in the New York version of the Iditarod. Another case involves the death of a kidnapper in an empty apartment and where is the kidnap victim?

Can knowing a secret be a motive for murder? The CSI team must figure out if a change in gender is cause for the death of a showgirl. Also Lindsay goes back to Montana to try to put the person who committed the murder of four friends behind bars.

Reed Garret gives Mac some interesting information regarding the death of a college student. Also the rest of the team will need to be a step ahead of Ava Brandt to figure out why a security guard was murdered.

Mac may have a difficult time solving the murder of a music mogul the sister cleverly uses a lie detector test to cover up the crime. Stella wonders if she has HIV due to an accident.

Danny and Mac have to go to Noah’s Ark to find out if a broken promise leads to his murder. Stella and Sheldon investigate the death of a man dressed as a cigarette. Stella hopes to have her job after not telling Mac that she may be HIV right away.

Illusionist Luke Blade may have to defend the art of magic after an illusion is thought to have killed two people.

Back in Montana Lindsay will need to take herself back to the time when she was fourteen to help her remember the crime that killed four friends in order to help convict of the person that killed them.

At a French Revolution themed fundraiser at the UN, specifically at the French consulate, Mac, Stella and Hawkes find themselves hurdling diplomatic road blocks investigating two murders. Meanwhile, Danny and Lindsay reunite on a “blinged” out cockroach that lead to murder.

The team finds itself investigating the murders of three different people, only to discover that two of the murder victims are linked and may have been killed by the same person. One of these cases becomes personal for Mac.

Trouble begins for Mac when Clay Dobson becomes a free man due to a mistake he made. Stella learns the results of her HIV test from Adam.

Mac believes he can fight the internal affairs investigation that is about to be started against him because of what happened to Clay Dobson. Can Mac explain what happened to the suspect he was chasing and will it be good enough for him to keep his job? Also Stella could lose her job as a CSI after a cold case is somehow connected to her.

Can the team clear a tennis legend of murder? Also Mac believes that the continuing investigation into what happened with Clay Dobson is nothing but media pressure. Can friends and colleagues help save Mac Taylor’s career before it’s too late?

Dopo che Flack e i suoi hanno fermato uno dei più grossi carichi di contrabbando di droga, alcuni degli spacciatori fuggiti all'arresto entrano nel laboratorio, dove era stata portata la cocaina