A pair of amorous partiers in a cemetery stumble across a dying woman wearing a Victorian dress. She is barely able to say "Devil did it" before she expires.
Back at the NCIS office, LaSalle tries to get Brody into the Halloween spirit; he's got big plans, and he's dressing up as the Baconator (half bacon, half Terminator), which does not impress his partner. Pride calls them out to attend the crime scene.
The victim is identified as Melanie Hermann, a Naval Staff Judge Advocate. She died of blood loss and has two apparent puncture wounds resembling bite marks on her neck. The team decides to investigate Hermann's case history and identify any possible defendants who might hold a grudge against her.
Pride's wife Linda shows up at the office to drop off a bag of Halloween decorations. To Pride's dismay, Linda says that she will not be joining him in their regular Halloween tradition this year because of their current estrangement. Pride is hurt, but he is called away to the medical examiner's office.
LaSalle and Brody interview Hermann's legalman, Petty Officer Jake Dern, who says that there were threats against her, but nothing they considered serious. He also tells them that she was scheduled to attend a party at a restaurant, but he didn't know if she actually went.
Sebastian informs Pride that he discovered a remarkable resemblance between Hermann's appearance at her time of death and an illustration of Dracula's first victim. Loretta offers additional disturbing information, as well: the bite marks were just for show, and the blood loss happened when someone crudely removed the victim's kidney from her body, sewing up the incision with a thread from the dress she was wearing.
The owner of the restaurant where the party occurred refuses to give any information, so Pride goes to the party's host: Councilman Hamilton. He threatens to publicly arrest Hamilton for obstruction, and Hamilton agrees to tell the restaurant owner to give Pride whatever information he needs.
Thanks to the security footage, the team learns that Hermann left the party alone at 9:15. Footage from other security cameras in the area reveals that she was followed by none other than Petty Officer Dern, her legalman.
They confront Dern with his lies, and he confesses to following her because he has a "thing" for her, which was not reciprocated. After he lost track of her in the street, he spent the rest of the night drinking.
Following Hermann's footsteps, Brody and LaSalle find a warehouse with blood, and a corpse stuffed into a freezer.
Loretta performs an autopsy on the second victim, identified as Navy Lieutenant Commander Joel Abram. He has been dead for three days, and his body contains Hermann's missing kidney.
The team discovers a connection between Hermann and Abram: they were both involved in the trial of Chief Petty Officer John Neville, who was sentenced to seven years in jail for the sexual assault of Denise Murdock. Neville claimed innocence, that there was witness coercion and evidence tampering, and had been released three months ago. They realize that the judge's final words were in fact "Neville did this".
Denise Murdock's mother is very worried about her daughter, who has been missing for days.
John Neville, meanwhile, tells the team not very politely to get lost, despite his son Jesse's attempt to calm him.
Local police locate Denise Murdock's car, which had apparently been run off the road. There were signs of a struggle, as well as a strange powdery substance that is later identified as gypsum, which is used in construction. There is also some of John Neville's blood in the car.
Linda returns to the office and offers comfort to Mrs. Murdock; she tells Pride that she will stay with her until her daughter is found. When Pride is called away to the M.E.'s office, she tells him to "Go! Learn things!", revealing that he picked that mannerism up from her.
Loretta and Sebastian make a connection between Abram's death and Frankenstein's Monster, with the additional organ from a corpse in a graveyard and the use of a stun gun on the neck to symbolize the electricity used to bring the Monster to life.
John Neville's shrink, Dr. Wilkins, arrives; he informs the team that Neville was into twisted horror fantasies, and it isn't long before the team makes the connection between the crime scenes and a horror anthology Neville had in jail. The third part of the anthology is Edgar Allan Poe's "Cask of Amontillado", in which the victim is bricked up alive in a cellar wall - which means were is a chance that Denise Murdock is still alive.
They search Neville's house and find the bloody knife, the stun gun, and Denise Murdock's driver's license, but no Denise. Neville is as defiant as ever and refuses to help them. Pride realizes that Neville's body is unmarked, making the blood in the car suspicious. They realize that the evidence was planted, and their suspicions turn to his son Jesse.
Jesse denies any knowledge of the crimes, even passing a lie detector test. Dr. Wilkins suggests he might be suffering from Dissociative Identity Disorder, and that his alter personality might be responsible. Pride and Brody provoke the alter to surfacing.
The alter admits that he killed Hermann and Abram and framed Jesse's father in order to send John Neville back to jail. Pride realizes that this alter personality was responsible for assaulting Denise Murdock in the first place, and that he had framed John. The alter then tells them where to find Denise.
They successfully locate Denise and rescue her in time. She is reunited with her mother.
Linda and Pride explain their mutual worries about Pride's work coming home with him or preventing him from coming home at all.
Brody gets into the Halloween swing by dressing as a Freudian Slip, and LaSalle cheekily teases her about flirting with Dr. Wilkins.