A serial killer taunts the CSIs by leaving them cryptic hints, and the longer it takes them to decode these puzzles, the higher the death toll rises. In the opening sequence the daughter of the first victim can be heard singing the "Ashes ashes all fall down" chorus from the Grateful Dead's "Throwing Stones".

When Horatio's ex-girlfriend is killed in an explosion, the team looks within their own department to find the killer. The team is uneasy as Eric returns to do some undercover investigation and evidence leads to the discovery of stolen diamonds in Ryan's house. They must find the real culprit and exonerate Ryan before things get out of hand.

When a suburban soccer mom is murdered, the CSIs uncover her family's dark past, while Delko continues his undercover mission. At the end of the episode, Caliegh confronts Delko of what's going on and an explosions happens soon after.

Evidence is stolen from the lab following a diamond heist and Eric Delko returns.

The spirit of a victim haunts Calleigh until she is able to solve his murder.

The CSIs work on solving three separate homicides that occurred during Spring Break vacation.

Horatio's son, Kyle, seeks his father's help in solving a murder.

The team does not have any difficulty finding suspects when a hated receptionist is murdered with an axe and her body is pushed down a evelvator shaft. The real difficulty is finding out who did it.

Horatio and Delko travel to Los Angeles to clear Cardoza of an evidence tampering allegation that threatens the prosecution in a current Miami murder case.

A dead body falls from the sky, and the team discovers that he had been a passenger on a private commercial space flight.

Horatio and the CSIs have just 24 hours to find out if a man on death row is truly guilty of killing his wife and young daughter.

A man is chopped in half, and the lab tries to tie the case to a Japanese mobster, who seeks custody of his biological son, who was adopted by the victim. Meanwhile, Natalia's hearing loss nearly makes her a victim during the investigation.

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

The team discovers that Delko is working for an attorney defending a homeless man accused of raping and killing a wealthy woman.

The CSIs investigate the death of a census worker, which leads to a high-speed car chase and an explosion that puts Ryan and Natalia in danger.

Horatio and his team investigate when deadly jellyfish are used as murder weapons. Meanwhile, a mysterious woman from Jesse's past unexpectedly shows up.

The CSIs investigate a horrible car crash to discover who or what caused it. The probe reveals the darkest secrets of the drivers involved.

Raymond Langston (Laurence Fishburne) from Las Vegas travels to Miami to aid a murder with possible ties to a human leg that was discovered in Vegas. This is the first part of the CSI: Trilogy.

A groom goes missing, and the CSIs recreate his debauched bachelor party to solve the case and a murder. In the meantime, former lab tech Walter Simmons joins the group as a new CSI.

A lethal outbreak in Miami that is linked to deadly farming practices is investigated as murder. Alexx returns to help the team with the case.

The CSI team are on the case of a repoman discovering a dead body on the plane he was supposed to repossess for his client.

Calleigh's testimony before IA may threaten Delko's future. Meanwhile three volleyball players mysteriously die during a game.

A gunman attacks the Miami lab and holds four people, including Cardoza, hostage. Horatio is to serve as the negotiator, where the gunman has a rather unique request in exchange for the hostages.

The continuation of last season's story; the team searches for Delko. Meanwhile, there is a flash back to 1997 when H brought the team together.