Andrew Hoffman is washing blood off in the bathroom sink when he receives a cell phone call by someone waiting outside to pick him up. He walks by a dead female body, lying on the floor with a large jagged cut across the torso, as he exits the home. The body, clad in bra and panty only, lies on a sheet of plastic with shoes, clothing, and a bloody pocketknife next to her body.
Hoffman enters the awaiting car and gives the driver, Ziva, a passionate kiss. As Ziva drives away from the house, Gibbs tells Tony, dressed in coveralls sitting in a service van across from the home, to enter the home. Gibbs and McGee are in a separate vehicle tracking Ziva via GPS. Hoffman is taking Ziva, who he refers to as Gina, on a mystery date. Apparently, this is an undercover sting operation.
Tony enters the house to hide surveillance bugs, but finds the dead body instead. He phones this fact to Gibbs, referring to her as victim number five. The victim's ring finger has been severed; a signature of the serial killer they are investigating. Gibbs decides to apprehend the suspect immediately; tells McGee to phone Ziva with the distress code word, "Bernard." Ziva tells the caller he has the wrong number and hangs up. Suspicious of her, Hoffman takes her phone to see the call ID lists "Gibbs." She passes it off as a wrong number, but he sees it as number 2 on her speed dial. Keeping her calm she says it was an ex-boyfriend. Hoffman pulls out and points a snub-nosed revolver at Ziva, forcing her to drive to an abandoned warehouse. Gibbs and McGee track down the vehicle to find it empty with no evidence indicating where they went.
Inside the warehouse Hoffman admits to killing the women for sleeping around on their husbands who were away fighting for their country. He forces her to the back of the warehouse where he intends to kill her. Ziva, gun pointing to the back of her head, hears the hammer of the gun being cocked and turns out of the bullet's path enough to avoid the full impact, but it grazes her right temple. Hoffman loses the gun during the struggle. As Ziva reaches for it, he pulls out a knife to stab her. Ziva fires five shots into him as he stands over her, causing him to fall onto her.
Gibbs and McGee hear the shots and rush in to aid a visibly shaken Ziva. Gibbs gives her the rest of the day off to seek medical attention, but she hangs around, insisting she is fine. Detective Steve Rosetti arrives at the warehouse crime scene, annoyed about being removed from the case to allow NCIS to investigate and take credit for the takedown. Later, back at the office, Tony tries to make Ziva smile by tussling her hair in a playful manner. However, she grabs his arm and twists it; clearly not in the mood for Tony's antics.
The identity of the fifth victim is still unknown; Tony and Ziva return to the Oyster Lounge, where previous victims were known to frequent, which was how they initially found Hoffman using Ziva as bait. She is familiar to many of the bar's patrons including Michael Locke, a longtime patron looking for his girlfriend, Devin, who disappeared three weeks prior. Ziva tells him the truth about her undercover status as Gina. She confirms to him that she is responsible for shooting Hoffman as reported by the news. Michael recognizes the fifth victim as Julie and is worried his girlfriend may have fallen victim of the serial killer.
A day later Navy Petty Officer Kevin Massey comes into NCIS headquarters to thank Ziva for killing the suspect; his wife was victim number four. Ziva has a flashback of Hoffman's killing.
Gibbs visits Ducky in autopsy, where Ducky has found an inconsistency in one of the murders. Victim number four's finger was cut off immediately after death, while the other four were dead for several hours before the amputation. Abby come in on rollerblades, justifying it by the amount of time she saves getting around the building quicker. She tells Gibbs she found a bloody partial print that does not match Hoffman's or the victims'; she theorizes that Hoffman has an accomplice.
Tony, in his usual juvenile way of showing concern for Ziva, continues to nag her. He offers to take her out for drinks, but she declines. He apologizes for the nagging saying he was trying to snap her out of the funk she is in. Ziva goes to the Oyster Lounge to relax on her own. Michael is there, still lamenting the loss of his girlfriend. Ziva decides to help find her.
Ziva arrives at work the next day despite being told by Gibbs not to come in. McGee finds evidence of a possible accomplice while reviewing the Oyster Lounge's surveillance footage of victim number three with Hoffman. Ziva thinks it may be a coincidence. Rosetti arrives at NCIS headquarters wanting to know why the investigation continues. Gibbs demands all of the evidence from Rosetti's case files despite his opposition to keeping the case open.
Ziva runs into Michael at the bar again. After some not so subtle flirting, they end up in his bed. As she sleeps, she mistakes his reaching over her to grab his glasses (on the nightstand next to her gun); she grabs the gun and points it at him. He pushes it away with his hand. She admits to being a former Israeli Mossad agent, which he takes to mean assassin. They patch up the misunderstanding and get back lovemaking.
Abby analyzes blood from inside the handle of the knife that indicates a blood type different than all the known victims or Hoffman. She and McGee deduce the potential of an unidentified sixth victim. Tony uses this information and finds out the unmatched, rare B positive blood type is the same as Michael's girlfriend, Devin. Arguing over Michael's possible involvement, Tony realizes she has slept with him.
Among the many boxes of evidence Rosetti brings, McGee find a page is missing from victim number three's address book where the R's would be. Abby determines from video analysis that the accomplice is about 6' 1" and 180 pounds. In a private conversation Ziva admits to Tony these measurements are similar to Michael's. She accuses Tony of jealousy for pursuing him as a suspect. Later, with the entire team present, Tony likens the situation to the movie Sea of Love, where Al Pacino, a cop, sleeps with Ellen Barkin, a serial killer suspect. He say the zany twist is Ziva is Pacino and Michael is Barkin. Both Ziva and Gibbs is angered by the reference.
Meanwhile, McGee compares victim number three's phone records to calls placed to persons with last names beginning with the letter R; Det. Rosetti's name is on the list multiple times. During interrogation Rosetti admits to tampering with the evidence to cover-up his extramarital affair with Monica Bishop, victim number three who he meet at the same bar frequented by Hoffman. Gibbs riles him up by accusing him of being Hoffman's accomplice. Rosetti claims to have hidden his relationship to keep from being thrown off the case and losing his shot to take down the killer. Gibbs believes him.
Ziva goes to autopsy to view Hoffman body; she has yet another flashback. Gibbs enters, encouraging her to move on from whatever is holding her back. She confesses she almost died because of her bad judgment with Hoffman in the warehouse. Gibbs tells her to trust her judgment, because the moment she doesn't, it won't be "almost."
Back at their desks, Tony lays out the circumstantial evidence against Michael Locke to Gibbs. Ziva steps forward with her gun, indicating Michael's fingerprints are on the barrel. Tony asks her what she is doing and she responds, "Trusting my judgment." Tony brings the gun to Abby, in the garage combing through Hoffman's car, for fingerprint comparison to the print on the knife. She finds a container in the trunk's spare tire wheel well, with four severed fingers which she and Ducky confirm are from victims one, two, three, and five.
Ziva brings Michael to the warehouse and recalls to him the circumstances around Hoffman death, again suffering a flashback. Back at Abby's lab the rest of the team determine that it was a copy cat, not an accomplice, with access to the knife who killed victim number 4, Patricia Massey. The copy cat could not have known to wait before severing the finger nor where to store it with the others. Also, Michael's print does not match the knife's bloody print, eliminating him as a suspect, leaving Patricia's husband, Kevin Massey, as the prime suspect. Gibbs says to always suspect the spouse; Ducky asks if that is from personal experience. Tony calls Ziva to confirm Michael in no longer a suspect. Michael overhears and takes offense; Ziva alleviates his concern that she was only interested in him as a suspect. He leaves unconvinced she is being honest with him.
Gibbs, McGee and Tony confront Kevin Massey at his workplace on a military base. They accuse him of hanging out at the bar connected to the first two victims, and following Hoffman home with victim number three. While Hoffman was away from his home, they say he broke in, stole the killer's knife, and used it to kill his wife in the same manner as Hoffman. Massey is taken into custody.
Ziva enters the Oyster Lounge to find Michael drinking his sorrow away. Ziva hands him a note with Devin's number, says Devin wants to talk to him. Michael thanks Ziva as she leaves. She looks back and smiles as Michael calls Devin on his cell phone.