Megan Donner returns to the CSI unit in time to work on a jet crash in the Everglades. While searching for survivors, they inexplicably discover a female victim found five miles from the crash site. When the only survivor says the woman opened the plane's hatch in order to commit suicide, Horatio is suspicious. The team must now recreate what happened on that fatal flight, especially when the pieces don't quite fit together.
A dead man with a slit throat and a partially burned face is discovered on a Miami beach, along with an unconscious young girl who was beaten and thrown into the ocean. The investigation leads Horatio to a prominent Florida family and its steely patriarch, who was once involved in a mysterious case that has plagued Horatio for years.
When a priest is found dead in his rectory after being brutally shot, Megan, Calleigh and Speedle must untangle a messy web of familial issues that lead to his death. Elsewhere, Horatio and Eric attempt to solve the emotional case of an exploded vehicle, which was home to a mother with child.
The whole team investigates the crime scene of an indoor amusement park when a young girl is found dead in the bathroom. They must track down the relentless man responsible for the heinous crime quicker than usual, as everyone on location has been detained until they can be cleared. What looks to be like a regular attempted kidnapping turns out to be much more than any of the detectives had bargained for.
Horatio, Calleigh and Speedle investigate the death of an exotic male dancer found dead after a sexual party, and must dig through the evidence to discover a motive. Meanwhile, Eric and Megan investigate the death of a man involved in diving that mysteriously died after climbing onto a random boat.
Horatio and his team must uncover the evidence in the brutal murder of an entire family in their own home. The only survivors are a blood-soaked toddler, and the father who's in surgery. The immediate assumption is that the mother is responsible – post-partum depression – but the evidence discloses a different outcome.
During a typical morning rush hour in downtown Miami, an unseen sniper chooses three victims at random and opens fire, killing each with a single shot to the head. Horatio and his crew rush to the scene, which is quickly mobbed by TV news reporters eager to spin the murders into a national story. The initial investigation doesn't reveal much, as there were no witnesses and little evidence remains. But the case heats up when the sniper strikes again, killing two more innocent people.
Horatio, Speedle and Calleigh root through the evidence in the homocide of a strange, and unorthodox college professor when they find him tied to a tree. Elsewhere, Delko and Megan investigate a car found in the water with a dead body in the trunk, and immediately suspect an insurance scam.
The team investigates the death of a young model, whose body was found near a juvenile detention camp for girls. Across town, Delko and Speedle probe the bizarre death of a man who was apparently burned from the inside.
Horatio and Speedle investigate the slaying of a hooker who is found dead under a bed in a plush beachside cottage, her naked body having been stabbed 23 times. But the crime scene yields few traces of blood because the killer bathed the victim in the cottage's tub with cardamom soap. Across town at an urban gas station, Calleigh and Delko attempt to uncover why a German tourist was gunned down in an apparent carjacking. They learn that a masked assailant approached a vacationing couple's rental car, shot and killed the husband, but left the wife unharmed and then fled the scene.
Horatio investigates the death of a man who accidentally inhaled a lethal combination of chemicals in a neighboring house after he went inside to retrieve his cat. Elsewhere, a resident of a retirement community is found dead in a pool of blood, an apparent victim of a vicious attack.
A nude man is found tied to his bed, having suffocated on a rag stuffed in his mouth while he was being sexually assaulted. Meanwhile, while investigating the murder of a crematorium owner, the CSIs discover dozens of bodies that were never cremated.
A dead junkie is found on a Miami street with a broken neck and a wad of cash in his hand. When the body is taken to the lab, Alexx notices that the victim's right hand is burned down to the muscle, even though it wasn't like that when he was found. It's deduced that he was exposed to radioactive material. The investigation leads Horatio to an environmental lawyer involved in radiation cases. Shortly thereafter, she learns that she is being eaten up inside by the deadly substance and has only days to live, but she doesn't know how she ingested it or who gave it to her.
Shortly before Horatio is set to testify at a high-profile murder case in which the defendant is the husband of a city councilwoman, he's given new facts that could prove the man is innocent. The information revolves around the discovery of a second victim who matches the profile of the first one and was killed in a similar manner. If the man on trial isn't guilty, then Horatio fears that a serial killer may be on the loose.
The investigation into a drug heist offers brief glimpses into the private lives of the CSIs, whose nerves are on edge when they become suspects in the crime they're trying to solve. A police convoy headed across town includes an unmarked truck filled with confiscated drugs being taken to an incinerator to be destroyed. The trip ends abruptly when thieves hijack the vehicle, kill its driver and shoot Speedle, who was riding shotgun. It's hard for Horatio when the media draw comparisons to a similar case several years ago in which his brother, an undercover cop, was killed. But it's worse for his team when Internal Affairs decides that one of them tipped off the robbers about the delivery.
Horatio battles the FBI and U.S. Marshals as he tries to uncover why a woman was murdered at the side of a pool at a hotel. The investigation begins shortly after the woman is found dead from two shots to the head. The evidence suggests that it was a professional hit man, which is strange enough, but the case becomes additionally puzzling when the Feds and U.S. Marshals get involved. Plus, the murder weapon is linked to a cold case that was orinially investigated by Yelina. Meanwhile, Calleigh talks to her dad about his drinking problem after she's called away from work to drag him out of a bar.
Horatio is approached by a parolee he helped put away several years ago, who begs for his assistance in finding his missing teenage son. As the investigation gets underway, Horatio discovers that the boy may be planning a deadly assault at his high school. Meanwhile, as Speedle investigates a man's death, the victim's flirtatious girlfriend, who was there when he died, tries to play on Speedle's obvious attraction to her.
The team investigates the deaths of two college students who were in Miami on spring break. The first is a teenage girl found dead on a beach with her neck broken and human bite marks on her legs. The second is a young man found in the bottom of a hotel swimming pool who apparently died before he hit the water.
Speedle and Delko are present when a trendy nightclub catches fire, apparently from a DJ's pyrotechnics display, killing sixteen people and injuring dozens of others. But the ensuing investigation reveals it may have been arson to cover up a murder. Meanwhile, Horatio probes the death of a prostitute whose body is found in the bathroom of a judge's home and evidence suggests that she was in the club during the fire.
An explosion in a rundown barn nearly kills Horatio and his crew just after they find a dead man inside, bound with duct tape. The case gets personal for Horatio when he discovers that the leading suspect knew his late brother. Meanwhile, Alexx is shocked to learn that her best friend's husband has been murdered, apparently the victim of a random shooting.
An inmate at a massive Miami prison complex is stabbed to death in the prison yard. Shortly after Horatio arrives on the scene, a helicopter appears above the correctional facility. He immediately fears that the murder was a decoy to set up an escape. That's confirmed as three prisoners hop aboard the chopper and flee. As the investigation gets underway, the identities of the fugitives become known and a horrible realization sweeps over Horatio: two of the escapees are cold-blooded killers who already have their next victims picked out, and the other is a child molester who he recently put away.