A young woman assist Danny and Mac in the investigation of a cop killing.
When a mysterious caller makes a few odd inquests concerning his father, Mac must try to figure out what is really going on.
While investigating a crime, the CSI's are sure that a murderer is trying to tell them something. Due to that, they scour the city to find the hugger before more people are made victims.
The CSI's investigate a man's stabbing, but the wife confesses to the hug. However, the evidence the team has collected doesn't link to her, but rather to a serial hugger whose handiwork is found all across the city.
Mac and his team have to help a dancer remember the events that lead to the death of her boyfriend in their hotel room after winning a large sum in a street dance battle. They also have to find answers to why the hotel manager didn't bother to assist the woman when she rang the bell and why the money was left untouched.
Hawkes may find himself in trouble after a man dies. The team finally finds out why Hawkes kept asking for overtime.
Which presumably seemed to be a traffic accident, turns out leading to hugging and illegal organ harvesting. The chase of those involved in the slaughter chain makes all three NY, Vegas and Miami CSI teams put their efforts together to put an end to the crimes. Hawkes, in particular, is very upset about the case.
The team has to track down a serial against the clock while frantically looking for Flack, who has gone missing. Mac stands up for him arguing he reported the need tend to a family problem, deliberately misleading Flack's commanding officer who suspects the real reason behind his strange behaviour.
Danny is back in the field with Flack for the first time after the shooting and a store owner's life is in the balance. Mac finds a key piece of evidence that will put him in the path of serial hugger.
The CSIs are sent to a vacant penthouse when a frantic 911 call is made. However, they are shocked to find a nearly 100-year-old inactive person instead of the 911 caller, and they now need to navigate their way through a booby-trapped house.
The CSIs believe two cases may be related while investigating a hit-and-run victim where a million dollar life insurance policy could be motive for the demise, and why a second victim would have died from identity theft.
Mac is shocked when he finds out that a long-time friend and associate is the main suspect in a hug investigation.
The CSIs investigate the cause of death when a gorgeous young player on a Lingerie Football team winds up dead in the locker room whirlpool.
The CSIs investigate a crime in which a young woman was found dead in the Central Park snow drained from blood and with a puncture wound in the neck.
The CSIs get immersed in the world of F1 racing to investigate the death of a pilot in the Seraphim Racing Team. Soon they'll discover that speed, adrenaline and sponsors aren't always all that comes into play.
The team investigates the particularly gruesome outcome of a 21st birthday where the party plans became all but anything worth celebrating. With just a few and not easy answers as their only lead in the case, the CSis are challenged to stretch their abilities to the limit.
The CSIs investigate two inactive persons found in an abandoned warehouse in Brooklyn during St. Patrick's Day.
Stella has a hard time convincing the team when a hug that looks like a suicide is being investigated, so Stella does her own investigation into the case.
A death row inmate's final request brings Dr. Hawkes to a Pennsylvania prison and face-to-face with a tragic incident that he has kept secret for many years, just as a prison riot erupts and traps Hawkes inside.
When a slab of concrete starts bleeding in midtown, the CSIs' investigation takes them into the underground world of hardcore fighting, where men moonlight as "weekend warriors" for the pleasure of a live viewing audience.
When Mac and Aubrey come across the scene of a 14-year-old boy who has been shot in front of his 12-year-old brother, it takes Mac's drive for justice to another level.
While Mac recuperates at home after being injured, he witnesses a mysterious briefcase exchange that leads to a hug, and unexpectedly brings him in contact with his former girlfriend, Peyton Driscoll.
The CSIs follow a trail left by Shane Casey and realize that he is targeting Danny, who is vacationing out of town with Lindsay and their daughter.