Federální agenti NCIS se právě připravují na kurz sensitivity, když jsou vyslání do Quantica, kde byly zavražděny dvě mladé Korejky. Navštíví místo činu, dům námořního seržanta Portera a jeho manželky Sun, která je jednou z obětí. Druhou je Min, manželka seržanta Kraina, který je služebně v Iráku a o tragédii ani netuší. Podle prvních známek musely oběti svého vraha dobře znát. Ženy byly zasaženy třemi ranami, výstřely zasáhly jejich srdce. Podle Mallarda je vrahem vycvičený profesionál, který je chladnokrevně popravil.

Agenti se od souseda dozvědí zajímavé informace. Sun to sice nikdy nepřiznala, ale její muž nadměrně pil, žárlil, omezoval jí, zakazoval stýkat se s přítelkyněmi a pravděpodobně jí i fyzicky týral. Prvním podezřelým se tedy jeví manžel Sun, pan Porter, ale je to falešná stopa.

Vyšetřování se přesune k manželovi paní Dawsonové, který se nedávno popral v klubu. Když si s ním vyšetřovatelé přišli promluvit, zjistili, že jeho žena právě zmizela. Ukazuje se, že všechny tři dámy pocházely z Koreje a vzaly si za manžely americké námořníky v Soulu zhruba ve stejné době, navíc je spojuje kontakt se stejným člověkem, majitelem restaurace. NCIS se obává, že příštím terčem bude Yoon Dawsonová a její malé dítě. Vyšetřování ale nabírá jiný směr, když se přijde na to, že ženy nepochází z Jižní, ale ze Severní Koreje.

Majitel restaurace tvrdí, že Dawsonová je severokorejská špiónka a že ženy zemřely proto, že o ní sbíraly na jeho žádost informace. NCIS varuje manžela, že se s ním Yoon možná spojí a bude ho chtít zabít. Ten však záležitosti s tajnou agentkou nevěří. Yoon se s ním skutečně spojí a ukáže se celá pravda.

This is the one where the North Korean spy kills off her co-spies and prevents a bombing. She is the only one of the 3 spies in a 'sleeper cell' who has fallen in love with her husband, had a family and adopted the US way of life. They each met a marine when the marines were stationed in South Korea and passed themselves off as South Korean, to marry and emigrate to USA. Our "good villain" kills the other baddies, knowing that it will reveal that she herself is an enemy of the state, so far as the law is concerned, even if she is doing it to protect the US from harm. And the husband, the father of her baby, is put in a position where he has to decide whether to believe in her no matter what, or to react to the fact that she has been a spy (and thus deceiving him at some level) from the start. When you are undercover, is everything tainted by the central lie?

There is a small red herring storyline concerning domestic violence in the home of one of the murdered Korean wives...but it wasn't the husband who was the violent one. In interrogation, Gibbs has to move from his antipathy towards men who hit women to realizing that sometimes the man can be the victim. This is a growth point for Gibbs.

recap:
A Korean-American mother (later we learn she is Yoon Dawson) and child are entering a house; their older neighbor helps them, they go in to find two other Korean-American women dead on the sofa. We learn they are Marine wives, Sun Porter and Ming Crane. As NCIS immediately determines and Ducky confirms more precisely, each woman has been shot three times. Suspicion immediately falls on Sgt Porter, who is known to be an abusive husband.

The team locates Sgt Porter; he is drunk in his car, and seemingly unaware he is not being arrested for drunk-driving. His gun is also the murder weapon. When interrogated, Gibbs is, to the others' surprise, sympathetic to him. Porter says he thinks his wife never loved him, and was out of his league but he protests his innocence. So then Gibbs becomes tougher. Porter claims it was Sun who was violent. There is also no powder residue on Porter.

Now NCIS speak to Dawson, and they find that Yoon (Mrs) Dawson has disappeared, believed kidnapped (The window in the room has been broken from the outside), though her baby remains. Dawson describes an altercation at the Officers' club where two officers hit on Yoon. But of course Porter could not have kidnapped Yoon, since he was already in NCIS custody when she disappeared.

Abby studies the three Korean women's computers and credit card records. She says she has nothing in common with them. But in the last month, all three had had regular phone calls from a payphone in a Korean delicatessen. All three worked for a catering company associated with that delicatessen. The previous night, Yoon called that shop with her cellphone, two hours before she was abducted. But the cellphone is still in use....and to call that payphone. So they stake the shop out. When Yoon's cellphone calls the shop, NCIS traces the call to the same neighbourhood. A Korean man is speaking at the payphone and Yoon Dawson then appears with a gun, trying to kill the man. Yoon disappears up a fire escape; NCIS apprehend the man (the shopkeeper), who had hired the three women to work for her catering company.

When questioned, the man (Mr Sung) says he suspected Yoon to be North Korean, because she uses pre-war words, and had asked the other two women to check her out. So it sounds as if Yoon was a secret agent. He blames himself for the other two women's death, sincee he had helped them integrate into the community. Sung is put under (protective) surveillance, having refused protective custody.

Ziva, who is completely unsentimental, makes all her analysis of the case on the basis of what a good spy would do, and predicts what she thinks the murderer will do. Could Yoon be a sleeper? If so, she would have changed her appearance and identity by now. Gibbs makes his analysis based on the reasoning that the woman is no longer just a sleeper spy, but now a mother and that her loyalties have shifted. Ziva distrusts this sentimentalism. Dawson can't believe his wife is a spy, until he sees the mobile phone photo of her holding a gun to Sung. The next minute, Yoon phones her husband up, and she tells him, ' No matter what they tell you, know that I loved you with all my heart.' Abby traces the call from the payphone, near the Pacific Rim Society event that the three Korean women had been assigned to as caterers with Sung's company.

Now we see Sung himself at the event, but Yoon appears and holds him up with a pistol. She asks 'Where is it?' and then shoots him in the knee. 'Where?' she asks him, threatening to kill him. Sung says it is 'In the truck'. At this moment, NCIS bursts in, and she tells them there is a bomb in the building. Ziva threatens to kill her in turn and so Yoon drops her weapon and reveals where the bomb is and that Sung is actually a North Korean agent too. She says she killed Ming and Sun in order to keep her family, but she's failed.

The bomb is revealed, but Yoon is the only one who knows how to defuse it. The team stands around rather than evacuate.Yoon succeeds.

In the final scene,Dawson gets to meet up with his wife Yoon, who, despite defusing the bomb and saving the team (and others) is now in custody and being escorted from interrogation in NCIS to wherever the CIA are taking her. We get hints that because Yoon sabotaged a whole spy cell and saved hundreds of lives by defusing the bomb, and has first hand intel of North Korean spy practices, she has a chance of a very good deal.

Gibbs gets the guards to stop so that husband and wife can have a minute together, in the squad room. Watched by all the team, the wife tearfully says how sorry she is and that she truly meant everything about how she loves him and their baby. And, equally distressed, clutching their baby in his arms, he says he will be waiting for her and they will face everything together. And Ziva learns another lesson about families that her own could never teach her.

This is one where the guest stars turn in a truly powerful performance with emotional tension that is gripping, right to the end.