When a man is found dead on the Brooklyn Bridge and the only evidence is his marriage proposal displayed in lights on a Manhattan high-rise and a souvenir key chain as a murder weapon buried in his chest, the team comes together to find the person who may have brutally rejected his offer.

Stella, Flack, Lindsay and Danny can't resolve how, despite the police being tipped off by the store's personnel, the women were able to escape the jewelry store so quickly. Also, Lindsay proves her strength when she puts herself in harm's way to solve the case. Meanwhile, when the mummified body of a city councilman's missing wife is found during a building's demolition, Mac and Peyton have their first professional argument when Mac isn't satisfied with her findings from the autopsy.

With thousands of suspects and no witnesses, the CSIs fight to collect evidence while spectators and marathon runners contaminate their crime scene. Meanwhile, a high-end vodka's ice-themed promotional launch party turns deadly when a model is stabbed, leaving Danny and Lindsay racing to collect vital evidence before it melts.

When a college girl is found beheaded at a sorority party, the entire team focuses on their toughest case yet. The victims wear t-shirts emblazoned with a logo inspired by Greek mythology that offers clues and hidden messages. By tracking the codes on the web, the team discovers that a serial killer is replicating the fate of mythological creatures by killing people in the same manner, and the only way to stop him is to unravel the hidden codes before he strikes again.

Danny and Lindsay work to find who bludgeoned a young woman to death after her performance with SuicideGirls and their suspect list grows smaller when the murder weapon proves to be a stiletto worn by one of the women. Meanwhile, Mac, Stella and Flack investigate the death of a homeless man turned streetballer who was killed after winning an intense one-on-one game in Rucker Park against one of professional basketball's best.

A young hotel concierge falls to her death from a balcony and is impaled on a statue shortly after an ugly incident with a popular model participating in a rooftop photo shoot. While Mac and Stella investigate the case, they hear gunshots coming from a nearby building and discover the shots came from a penthouse loft. When they enter, they find a woman standing over two dead bodies, one of them her husband. The woman claims the other victim was beating her husband, so she shot the man.

Mac, Sheldon, Jennifer, Peyton and Lindsay investigate the mysterious death of a party-goer found in a subway car where the victim initially appears to have bled out, but the cause of death is determined to be multiple organ failure. The team must track the promoters of the subway raves to find what killed the young woman before another victim is found dead at one of their secret gatherings. Meanwhile, when one of New York's most eligible bachelors is found dead in the swim gym of his penthouse apartment, Stella, Det. Flack and Danny question his room maids, beautiful women hired to clean the homes of the wealthy in exchange for room and board.

When a professional paintball player is shot in a warehouse, the team assumes the murder was committed by an opposing player who took the game too far. But their investigation becomes more complicated when his opponent goes missing. The evidence at the scene proves to be black cocaine originally confiscated in a raid by the police department months before, and Mac's suspicions of an internal leak causes friction within the department. Meanwhile, Stella grows increasingly paranoid when she suspects that she's being followed.

Five days after surviving a horrific car accident, the woman who lost control of her car while driving home drunk is murdered in her hospital room shortly after coming out of a coma. Despite being paralyzed from the waist down, the doctors gave the victim a good chance for recovery, so the team must determine who wanted her dead in spite of her prognosis. Meanwhile, Sheldon returns to the hospital where he once worked as a promising surgeon and his investigation opens old wounds that led to his departure and caused him to become a medical examiner.

While filming a promotional spot, a base jumper plummets to his death after his parachute is punctured by pigeons, leading the CSIs to the competitive world of pigeon racing and to a second victim, a prominent trainer who was also murdered.

The CSIs are floored when Sheldon Hawkes is apprehended during an early morning run as the primary suspect in a bartender's murder. While he maintains his innocence, Mac and the team grow increasingly frustrated when they are removed from the investigation for fear they'll contaminate the evidence. With a mountain of evidence stacked against him, the team works tirelessly on their own to piece together the clues that will hopefully prove Hawkes' innocence. Meanwhile, Danny and Stella investigate what seems to be an overdose, but they realize their routine case may be connected to escaped serial killer Shane Casey.

When an intruder breaks into the home of a deaf family and fatally shoots their teenage daughter, Mac works with the grieving mother who relies on her other senses to provide clues that will help catch her daughter's killer. Along the way she also provides assistance to Mac as he struggles in his relationship with Peyton. Meanwhile, Stella and Danny investigate when a professional ice skater is killed prior to competing in the U.S. ice skating regionals and whose body was found by her best friend, an Olympic skater who thinks she might be to blame for her death. Also, when Lindsay abruptly walks away from a crime scene and loses control of her emotions, the team questions her past.

The rules of the Idiotarod race encourage teams to sabotage their enemies' carts, so once the cause of death of their victim is proven to be multiple blows to the head, Danny, Sheldon and Det. Angell work to determine if this fun annual challenge became too competitive for one team. Meanwhile, when a successful real estate agent is found dead inside a Manhattan brownstone by some young kids, Mac, Det. Flack, Lindsay and Stella investigate what appears to be a possible kidnapping turned deadly.

A celebrity impersonator, who performed at a party in a ritzy hotel, is found dead in a men's room stall. She was drowned in the toilet. The investigation reveals the victim confronted a congressman, at another hotel event, shortly before being murdered. Across town, a man's body is found inside of a city salt truck. Also, Lindsay is asked to testify in a multiple-homicide trial in Montana. She was the only witness to the murders of four of her friends.

While investigating the death of a college student found dead in a Queens park, Mac, Sheldon and Det. Flack discover a secret college society that may have been behind the victim's murder.

While looking into the murder of a music executive, Mac is thrown off by the victim's sister who passes a lie detector test and swears that both she and the victim were attacked by a woman, despite the fact that the victim's sister would have been given his lucrative life insurance policy. Meanwhile, Danny and Detective Angell investigate the death of a woman in a bathtub.

Mac, Danny and Flack are puzzled by their latest crime scene, which includes an ark in the victim's back yard full of people, food and animals. Interrogations reveal that the people believed the apocalypse was near and the victim promised salvation.

Stella and Mac investigate a magician's trick that leaves a woman sawed in half. The only clue is a fingerprint on the trunk the victim was killed in and the print belonging to her stalker. But the suspect has an airtight alibi since he was at a court ordered, anger management class at the time of the murder. Lindsey is in Montana for the court case of her best friend's murderer.

Mac and Stella run into a diplomatic dead end while investigating the murder of a girl's professional handler during a fundraiser at the U.N.

The CSIs investigate three separate but equally bizarre cases -- a man is found in medieval armor impaled by a lance; another is found stabbed with an ice pick; and a body is stolen from the coroner's van.

When Mac arrests a police office, an alleged serial killer is set free, forcing Mac to take the issue into his own hands.

Stella must cope with painful memories when Det. Valens informs her that her DNA has been linked to a Philadelpia cold case.

The CSIs are puzzled when both evidence and witnesses name John McEnroe as a murder suspect, but he has an air-tight alibi.

Following the biggest drug seizure in New York history, Mac, Stella and Hawkes have to save their lab when the drug lord and his crew arrive to reclaim their drugs. In the action, two CSIs are taken hostage.