|Original Airdate||December 19, 2005|
|Previous Episode: Shattered|
|Next Episode: The Score|
Payback is the eleventh episode of season 4 of CSI: Miami.
Horatio hunts for the man responsible for a brutal rape on a woman years back, after new DNA testing technology finds the convicted rapist innocent. Alexx tries to find the surgeon responsible for a young girl's death after she finds a sponge in the wound.
DNA evidence from Natalia Boa Vista's work has exonerated a man named Brian Lexington, a man who was convicted of raping a woman named Valerie Naff, in her bedroom. Valerie is distraught at the reversal, and asks Horatio who raped her if Brian didn't? Horatio is determined to find out. Calleigh isn't impressed with Natalia's touting the case to the press--she thinks it makes the lab look bad as people will assume they were incompetent when in fact the kind of technology that exonerated Brian wasn't in existence when the case was originally investigated. Brian confronts Horatio and tells him he's going to sue the lab for malicious prosecution. Calleigh and Ryan reopen the case: Valerie had just moved into a new house when she was raped. Brian had been one of her movers, so the CSIs turn to other likely suspects. In the morgue, a tech brings the boy of Kelly Gerber to Alexx. Kelly was in a car accident, but her wounds don't look bad enough to be fatal. Alexx notes a recent appendectomy scar and when she opens Kelly up, she discovers a surgical sponge in her body that caused an infection, killing her.
Ryan shows Calleigh some silver shavings he found on Valerie's pajamas--graphite that could have come from the new locks. Calleigh talks to Phil Cobb, the locksmith, who repeats what he said during the original investigation: he installed new locks and left Valerie with three keys. Calleigh leaves with a DNA sample. Delko runs into Natalia in the hall and tries to return a bracelet to her that he found in his couch and assumes she left from the night before, but she tells him it's not hers. Alexx interrupts to tell Eric about Kelly Gerber and asks him to look into the case. Delko tracks down Dr. Brent Kessler, the man who performed the surgery, at the hospital and questions him, but the doctor is harried and barely remembers the surgery. After Kessler leaves, Eric takes the glass he was drinking out of.
Natalia tells Ryan the sample from the locksmith didn't match the sample from Valerie's pajamas, but she gives Ryan a new lead--the key ring from Valerie's house only has two keys on it meaning one is missing. Natalia recovers epithelials from the key ring and matches them to the pubic hair found on the pajamas, indicating that the rapist took the key. Horatio pays a visit to Valerie and discovers her fighting with Brian, who has come to her house. Horatio chases him away and asks Valerie who else might have her key. He asks about her boyfriend, Doug, but Valerie says she started dating him after the rape and hasn't given him a key. At the morgue, Dr. Kessler, clearly agitated, confronts Alexx about sending Delko to question his work. Alexx tells him about Kelly's death and he says he stepped out in the middle of the surgery and tries to pin the blame on the scrub nurse.
Calleigh and Ryan go back to the crime scene photos from six years ago and notice a framed picture of Valerie's house on a ledge--a gift, Valerie tells them, from her real estate agent, Jeff Colson. Colson refuses to turn over his DNA, so Tripp gets a warrant, but when he and Horatio go to an open house Jeff is hosting to serve it, they find Jeff dead. Horatio looks at real estate photos of the house and notices a sculpture is missing from the room Jeff was killed in. Alexx examines the body and says the beating was overkill--the blows to the head alone would have killed him. Horatio pays a visit to Valerie and tells her Jeff was the rapist and gently asks her about her whereabouts at the time of his murder. Valerie tells him she was home alone. Calleigh tracks down Valerie's boyfriend, Doug, on his boat and is immediately suspicious about his swollen knuckles, but he works in construction and tells her injuries are part of the job. Doug denies any involvement in Jeff's murder, but Calleigh tells him not to leave town.
Tripp, concerned about news of the warrant for Jeff Colson leaking out, confronts Natalia, who denies talking to the press. Ryan tells them the department may have a mole, and Natalia confirms that Jeff's DNA matched the pubic hair on Valerie's pajamas--he was the rapist. Delko analyzes the glass Kessler was drinking from and tells Alexx most of the contents were vitamin supplements. Alexx suspects the combo was being used to hide ecstasy use, but when Eric tells her about his sister's use of marijuana for medicinal purposes, Alexx recalls how Kessler was sweating and shaking when he came to see her. She confronts him: Kessler is in the early stages of Parkinson's disease, and is using ecstasy to keep the tremors under control. He tells Alexx he's still saving lives and that he's not ready to stop operating, but Alexx shows him the autopsy photo of Kelly and tells him the time to stop has come.
When Valerie recants her accusation of rape against Brian, Horatio realizes she's joining his lawsuit against the department. Knowing how fixated Brian is on Valerie, he suspects he may have killed Jeff. Alexx shows Horatio that Jeff died of inter-cranial hemorrhaging, but says his killer may have been impaired in some way, as the blows weren't as powerful as the murder weapon indicated they could have been. Horatio thinks it's Brian, but when his lawyer George Hammett brings him in, it's clear that despite being stabbed in prison, Brian's mobility isn't limited. Tripp realizes that George has a messenger on the payroll and that's how he found out about the warrant for Jeff. Hammett was hoping an arrest would increase his chances of winning the lawsuit against the county. Horatio's suspicions turn to Doug, but while they are questioning him, he realizes the killer didn't have limited mobility but limited upper body strength. A woman killed Jeff Colson: Valerie Naff. A sympathetic Horatio goes to Valerie's house and she tells him that no amount of money could make what happened to her right, and that when she discovered the truth, she saw his face everywhere. She confronted him and beat him to death. While Horatio can't offer approval, he does sympathize with Valerie and promises to be with her every step of the way.
- David Caruso as Horatio Caine
- Emily Procter as Calleigh Duquesne
- Adam Rodríguez as Eric Delko
- Khandi Alexander as Alexx Woods
- Jonathan Togo as Ryan Wolfe
- Michael Shanks who appears in this episode as Doug Stets is best known for his role as Dr. Daniel Jackson in the long-running Canadian/American sci-fi series, "Stargate SG-1".