Horatio investigates the murder of a model intentionally run down outside of a Miami hotel by a driver who fled the scene. When the evidence leads to a suspect, governmental red tape puts an unexpected twist on the proceedings. Horatio and Yelina begin to confront their feelings for one another.

A police officer collapses and dies after pulling over a car, and the investigation reveals he was murdered. Horatio grows suspicious when Internal Affairs gets involved in the case, leading him to believe that the killing wasn't a random crime. Meanwhile, Calleigh aids an abused woman who is living with one of the suspects in the probe. Yelina begins dating Horatio's nemesis – who is heading up the Internal Affairs inquiry.

An adult film actress is found strangled in the park and the CSIs must find the killer. Blood and human tissue are found under Ashley Anders' nails and the DNA matches that of the CEO of the company that distributes her films – and he's a registered sex offender. Also, Calleigh discovers his answering machine audiotape on which he makes a threat against Ashley. However, there is an accident back at the lab with this crucial piece of evidence and Delko was the last person to handle it. Now, IAB's Rick Stetler is put on the case, much to Horatio's dismay, as the CSIs try to uncover further evidence in order to find the girl's killer.

After a large yacht slams into a major Miami bridge, the team finds that the man steering the boat was shot and killed before the accident. The victim's wife reveals that their son had been kidnapped and her husband was handing over the ransom – three million dollars worth of jewels. But when the team learns that the jewels were fake, the investigation leads them into a dangerous situation at a jewelry shop that may contain crucial evidence, where Horatio must face the unimaginable when one of the team is killed in the line of duty.

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.

The wife of a famous baseball player is brutally killed in her home and her philandering husband is charged with the crime. The jury on the case, as well as the accused and his defense, visits the house to examine the crime scene, but when the lights are dimmed, as they were when the victim was killed, and then turned back on, the ball player is found dead with a meat clever in his back and a note that reads "guilty." Now, as Horatio and the team find that the husband's defense team tampered with the crime scene, they must examine the evidence to find the couple's killers. Meanwhile, Horatio gets a call from Yelina, who tells him that her son, Ray, Jr., is missing.

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.

The CSIs must investigate when a pedestrian is killed after a man falls from a building and lands on him. Horatio and the team find that the victim found on the sidewalk is not the same man who fell from the building, but the unfortunate person he landed on. The CSIs discover that the fallen victim is in possession of a sex DVD involving a top Miami criminal judge and a woman with a sordid sex life. When the woman is found dead, the team must delve into the complicated personal lives of those in Miami's judicial system in order to find the killer.

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.

An axe murderer on death row is given a stay of execution just moments before it was to take place, on the grounds that there may have been tainted DNA analysis used at his trial. Now, without using any DNA evidence, the team must race against time and reexamine all of the physical evidence in the case, just as they get a call on a new double murder that looks suspiciously like the case they're working on.

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 search of a missing 17-year-old girl, whose trip to Miami turns into an ongoing nightmare.

The CSIs must race against time when all evidence in a murder case points to Horatio. When a murdered woman is discovered, Horatio admits that he was seeing her and that he was the last person to see her alive. Although the evidence logically points to Horatio as the killer, our CSIs must now dig deeper to find the real killer and learn who would have the motive and the method to frame him.

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.

A drug lord is gunned in his Coconut Grove mansion and a suspect arrested at the scene claims he sells marijuana to Delko. Stetler, from Internal Affairs, investigates and the case quickly gets personal when Horatio gets involved. As for the shooting, the CSIs learn that two gunmen may have been involved. Also, Calleigh makes a major decision concerning her job.

After a group of wealthy women are robbed at a luxury day spa, evidence leads the CSIs to believe that this is a part of a much larger car chopping scam and each of these women are being targeted for a home robbery. Matters become worse when Horatio discovers that Marisol was also at the spa during robbery and he must now protect her when her life is threatened. Meanwhile, Ryan must deal with the fallout after he freezes during a shootout.

Calleigh is run off of the road in to a canal and causes freshly collected evidence to be compromised. The team must work to find new evidence, as most of the water-damaged evidence is unusable.

Evidence suggests a victim may have been set up as bait, after he's found to have been attacked and killed by a black bear. It's discovered the killer may have been trying to hide another murder - that of a high priced hooker and her bodyguard, who were part of a prostitution ring catering to elite Miami clients.

When one of Horatio's team lets their personal problems contaminate the investigation involving a spurned ex-lover, Horatio has to fire that team member.

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

Stalkers turn an innocent teenage swimming star into a sex symbol plasting photos of her over the internet. When following her it is discovered Horatio may be in danger after his testimony in a grand jury.

The murder investigation of a sports legend has complications when his body is lost by the lab.

Strange events begin to happen as the CSI team tracks down a serial killer who killed during a solar eclipse.

The investigation into a runway model's death leads Horatio to his son and his nemesis.

A serial killer is on the loose with a craving, making Calleigh its next victim, which also jeopardizes her ability to do her job.

The murder of a bride at a wedding leads the CSI team to a strip club as the investigation progresses.

In the first of a two part episode, Horatio once again has to tangle with his ex, Julia, who has it out for him. Someone is out for Calleigh, and is compromising their investigation in the process.

When a man is killed due to a fake 911 call, Horatio must face off with a private investigator who is systematically destroying the team. The PI also digs into the team's personal lives and gets both Calleigh and Eric pulled off the case.

A murder case involving extreme plastic surgery leads Horatio to Ron Saris, who is alive and seeking revenge on Julia.

The CSIs investigate the case of a man boiled alive, Julia spirals out of control, and one of the team's darkest secrets comes to light.

Horatio takes point as the negotiator when an armed gunman storms CSI headquarters and takes hostages.

Three volleyball players mysteriously drop dead on the court while Calleigh's testimony against Delko threatens his future as a CSI.

When America's sweetheart, Phoebe Nichols, bursts into flames during a concert, the CSIs expose the dark side of pop stardom.

A seemingly perfect jewelry heist ends in murder and when crime scene evidence is stolen from the lab, and Delko returns to find the culprit.