In Rio, Horatio and Delko are close to catching Riaz, Marisol's killer. There, Horatio reunites with Yelina and learns that his brother Raymond is in too deep undercover in a drug ring run by Riaz. To make matters worse, Horatio's nephew, Ray Jr., is working as a drug mule for Riaz, smuggling drugs into the U.S. Now, with the stakes set high, Horatio must catch Riaz before he takes the life of another member of Horatio's family.

After collecting the evidence to a crime scene involving a murdered ATF agent who was working undercover, Calleigh is run off the road into a canal, corrupting her evidence. Since almost none of the evidence is salvageable, the CSIs must work to uncover new, untouched evidence in order to solve the case. Meanwhile, Calleigh's ex-boyfriend, also an undercover ATF agent, offers interesting, yet conflicting, insight into the investigation.

Horatio and the team discover that the motive for the murder is tied to a 'death pool,' in which players legally bet off-shore on when famous people are going to die. However, the off-shore gaming ship proves to be not as legit as originally thought when the CSIs discover that counterfeit hundred dollar bills are being circulated as a result.

A male model is run over by a car and the CSIs discover that his good looks may have cost him his life. But when another male model falls to his death, Horatio and the team must find their connection before another murder occurs. Meanwhile, Natalia's abusive ex-husband is released from jail and begins stalking her at the lab.

A local city councilman's body is found in an empty house and the CSIs learn that neighbors were irate that the victim had been backing eminent domain, the government's right to force people out of their homes for private development. However, after Horatio learns that the judge hearing the case is not only dirty, but has a grudge against him and the lab, a new piece of evidence is found in the neighborhood that just may break the case wide open.

When a believer in Santeria, a mix of Catholicism and African voodoo, is found murdered in front of her shrine of animal sacrifices, bizarre incidents start happening around the CSI lab and people start speculating that the lab is cursed. However, the case takes an unexpected turn when the CSIs discover that the victim may have been murdered over a tangled plot involving stolen gold.

During evidence collection, the CSIs enter the world of sideshows, where kids gather in tricked-out cars, mostly stolen, performing dangerous stunts. However, when Horatio discovers that the victim's car's hydraulics where tampered with, he detects that the accident may be been staged as a diversion to a more serious, yet lucrative, crime.

After one woman is found murdered and another kidnapped, evidence leads the CSIs to uncover dozens of photos of unidentified missing women in a safe. After examining DNA, the team discovers that the kidnapping victim is none other than Boa Vista's sister, Anya. Now, as they try to locate Anya and the other women, Horatio and the others must find the killer who has been posing as a photographer to trap unsuspecting women before he strikes again.

Horatio uncovers a deadly plot against the City of Miami after a young woman is murdered at a charity event.

A Marine recruiter is found dead on a civilian shooting range with several bullet holes in him, but there's no blood at the scene. The investigation reveals the victim was dead before he was shot and that his body was dragged onto the range. As the case progresses, Horatio learns the murder may be connected to the death of a marine in Iraq who was killed in combat. Also, Natalia is shocked to learn that Nick asked Valera out and that she accepted.

A suspected terrorist, on trial for her part in a thwarted attack on Miami, escapes after an attempt is made on her life by members of the terrorist group with which she is associated.

When Natalia's ex-husband is murdered, evidence suggests that she killed him.

Tripp steps on the land mine while investigating the death of a Cuban refugee who is killed by one after stepping on shore. Now, Horatio and the bomb squad must work to defuse the mine before it detonates. Meanwhile, after protecting a woman in the midst of a domestic dispute with her husband, Delko is slapped with a $250,000 law suit by the wife who set him up.

When a truck full of confiscated weapons is hijacked and the weapons are released back into the public, Horatio links the crime to Clavo Cruz, a man he put away for murder years ago. However, on the day of Clavo's arraignment, a confiscated missile is launched into the courthouse to aid his escape, with Alexx inside. As the team tries to find Clavo and put him away for good, another member of Horatio's team is fatally shot.

A member of the team is pronounced dead after being shot in the head, not wanting to give up, Horatio has the CSI rushed to the hospital and watches as doctors try to bring him back. Meanwhile, the CSIs find evidence that could lead them to Clavo Cruz, the man behind the shooting.

The CSIs investigate when the parents of a baby sitter in an upscale neighborhood are murdered. As the team sorts through the neighbors' secrets and lies, they find an unexpected love triangle as a motive for murder. Meanwhile, a key piece of evidence found at the crime scene leads Horatio to expose a doctor with some dirty secrets of his own.

A men's hunting weekend turns deadly when one of the group is mauled by a bear and evidence suggests foul play.

When a wealthy real estate developer is killed, the CSIs suspect his wife and her two secret twin sisters -- who share the same DNA. The victim is killed at a charity event hosted by his wife. However, evidence soon reveals that the victim is not who they originally thought and blood found at the crime scene could belong to the wife OR her two secret twin sisters, who even her husband knew nothing about.

After a scalped body is found near a Native American casino, Horatio believes that the owners of the Casino and the County Supervisor may have had some involvement in the murder.

A young male star of action movies is discovered in the trunk of a stunt automobile. It becomes clear that his body was dumped in the car. The trail leads to a fancy rehab where it appears that he may have committed suicide. As the evidence mounts it becomes apparent it was homicide.

A wealthy Star Island couple's ugly & messy divorce results in a wave of violence, tragedy and death. As the body count rises, the couple's self-absorbed bickering escalates as Horatio grows more disgusted with them.

While Horatio investigates a case of revenge on a scorned ex-lover, a CSI's personal problems taint the investigation and Horatio is forced to fire a member of his team.

After a suspected carjacker is murdered, the CSIs learn that the victim may have been involved in drug smuggling off the shores of Miami with a very dangerous drug lord.

When a serial killer suspected of killing young women and branding them with a 'Y' is caught and also identified as having the extra Y chromosome, the 'criminal gene,' the team feels that they have closed their case until the killings begin again.