A young woman is thrown over the railing of a parking garage, but the investigation into her death uncovers evidence that she was killed before the fall and had likely been kidnapped. The victim's watch is traced to her boyfriend, who tells the detectives that she was a thrill seeker who was abducted during the course of an extreme kind of role-playing game. Meanwhile, Delko gets into trouble when he inadvertently interferes with a case after stumbling across a car-theft ring.

Horatio is quick on the scene when an armored truck carrying $3.2 million is robbed in a daring downtown heist. During the holdup, the driver is killed and Horatio guns down one of the two thieves. The other escapes with the loot, but the money turns out to be counterfeit. The team must figure out what happened to the bank's money before it was replaced with fake bills. Making the day even worse for Horatio, Yelina spies him with his niece and assumes the girl is his illegitimate child, not her own late husband's daughter.

A woman is killed during a posh party at an exclusive waterfront estate when a man opens fire on the proceedings from a cigarette boat. When a former con is arrested, he acts as his own lawyer and proves to be smarter than he appears. Complicating matters is the fact that the leading witness in the case is the dead woman's 10-year-old son, whom Horatio wants to protect, refusing to let him testify.

As a huge tsunami heads directly towards Miami, a ten-hour warning gives citizens just enough time to evacuate the city. In the chaos, two people are killed in a parking lot and the evidence leads Horatio to discover a plot to rob a bank timed to take advantage of the evacuation. However, as the CSIs close in on the robbery already in progress, they find that it's a more elaborate crime than they previously thought. In the wake of the storm, Ryan and Alexx discover a body washed up from a local cemetery that may have a different cause of death than originally recorded. Meanwhile, Horatio suspects that Yelina is being physically abused by her boyfriend, IAB's Rick Stetler.

Evidence leads the CSIs to believe that someone started a massive fire in the Everglades in order to cover up a murder. Local prisoners are brought in as free manpower to help fight the wild fire in the Everglades. However, when a serial killer escapes the scene, Horatio must track him down before he strikes again. Meanwhile, the body of a local college student is found shot to death and the fire has destroyed the crime scene and the evidence. However, when the team uncovers an illegal moonshine operation and homemade ammunitions in the vicinity, the CSIs uncover the real reason why the boy was out there.

Horatio's life is changed forever when he learns important information about his deceased brother. Horatio must now figure out what to do with this information about his brother, Raymond, and whether or not to tell Yelina. Meanwhile, the team investigates when a woman is murdered at a crowded bar after she's approached by a female employee of a service that helps men pick-up women. Also, when Delko loses his badge after some reckless behavior and it's used in a crime, he must locate the badge before it's used again.

The team must find the connection between the two crime scenes; the killing of a drug dealer and the rape of a well-off family member.

The CSI's are called out to investigate the murder of a young woman who was about to sign her divorce papers. Soon the husband turns out to be the ideal suspect. The only strange thing about the case is the murder weapon: a nailgun. The case becomes complicated when one of the CSI's is attacked when he returns to the crime scene and ends up in hospital.

When Horatio's nemesis, Walter Resden targets someone close to him, Horatio tries to stop him. Also Eric Delko's relationship with Natalia is tested when she thinks she may be pregnant.

The team is sent to investigate the death of a local celebrity, who is found murdered in her bathtub. The list of suspects includes her musician boyfriend, her assistant and her rival. The search for a young abducted girl is triggered, and Horatio tells Delko of Marisol and his plans.

A murder and kidnapping becomes personal when DNA from a crime scene reveals that Natalia’s sister Anya is one of the kidnapped women they are looking for. The team finds a safe full of photos of missing women and they must find the photographer who was using his camera to lure the unsuspecting women.

A truck carrying weapons that were confiscated from previous crimes are now back on the streets of Miami. An old enemy of Horatio's puts the lives of two CSI's in harms way after a confiscated missile is launched into courthouse allowing Clavo Cruz to escape during his arraignment and injuring one CSI and the fatality of another CSI.

Horatio has Eric rushed to the hospital and watches as the doctors try to revive him. The rest of the CSI team finds evidence that may lead them to Cruz.

There's a serial killer on the loose marking all of his victims with a Y on their chests and one or more of the csi's lives are in danger in this season 5 finale

The team investigates the puzzling death of a student and find evidence that Tim Speedle may not be dead.

After a body is found in a sinkhole, the team's investigation into the victim's death leads them to a robbery where the target is keeping a shocking secret.

The CSIs make a shocking discovery about their murder victim, while Horatio tries to save his son from Julia's erratic behavior.