Za Gibbsem do kanceláře přijde poručík Roy Sanders, aby ho požádal o vyšetření vraždy. Na Gibbsův dotaz čí vraždu má vyšetřit, odpovídá, že svou. Doktor Mallard provede Sandersovo vyšetření a zjistí u něj radiaci. Sanders je inspektorem Agentury pro atomovou energii. Jeho poslední inspekce byla v elektrárně v Brazílii.

Gibbs s DiNozzem začínají vyšetřovat v Agentuře. Pomáhají jim Sandersovi spolupracovníci Ruziová a Sadowski, kteří byli spolu s ním na inspekci v Brazílii, ale nejsou zasaženi radiací. Abby zkoumá dozimetry všech tří inspektorů a zjistí, že Sandersův byl poškozený, zřejmě sabotáží. Mezitím je Ziva pověřena dohledem nad Sandersem v nemocnici. Postupně si k němu vytváří přátelský vztah. I přesto, že je Sanders pod neustálým dohledem Zivy, jeho stav se zhoršuje, jako kdyby ho někdo neustále intoxikoval.

Sadowski je prvním podezřelým. Doktor Mallard však prokáže, že Sadowski je nevinen a navíc se u něj projeví příznaky nemoci z ozáření. Mallard přijde i na způsob jak byl radioaktivní materiál do Sandersova i Sadowskiho těla dopraven. Někdo otrávil thaliem Sandersovi cigarety a Sadowski pasivně vdechoval kouř, když byl se Sandersem na střelnici.

Zatím neznámý útočník se snaží ohrozit Agenturu pro atomovou energii. Gibbs zjistí od Ruziové, že další inspekce měla směřovat do Ruska, Pákistánu a Uzbekistánu. Mise byla ovšem tajná, nikdo se nesměl dozvědět kam jedou, ale někdo to přeci jen zjistil. Gibbs přes satelitní záběry zjistí, že v jaderné elektrárně v Uzbekistánu se snažili rozebrat něco, na co by inspekce neměla přijít. Někdo z Agentury jim dal informaci o plánované inspekci a snažil se vyřadit Sanderse z inspekce. Gibbs rozkáže Timothymu, aby prověřil bankovní konta všech zaměstnanců Agentury. Timothy narazí na Holly Stegmanovou, které v poslední době přišlo na účet větší množství peněz. Je jen otázkou času, kdy jí chytí.

Scene opens on the squad room with Ziva and Tony sussing out the details of McGee's new jacket. It is Armani and they want to know the price. Ziva's photographic memory assists: she had a glance at the label. They find it online, priced at $1,995. Gibbs takes his place at his desk. McGee finally arrives, followed by a tall, thin man. As they walk over towards Gibbs' bullpen, the man doubles up with a coughing fit, grasping at McGee's arm to keep his balance. McGee politely enquires if he is alright. The man proceeds to be introduced to Gibbs. He is a Lieutenant working for the IAEA on nuclear installation inspections (looking for safety breaches and illegal trading of plutonium and nuclear weapons materials). The Lt. says that he wants to report a murder. "Whose?" asks a laid-back Gibbs. "Mine" says the man, pulling clumps of hair from his head.Ziva, meanwhile, is dumbstruck by the sight of the visitor: she feels she knows his face.

The story unfolds that the Lt realizes that he has been exposed to radiation. He recently returned from Brazil on an inspection tour with two colleagues, a man and a woman. His radiation tag - that should register exposure to excessive radiation, - does not show exposure yet he is ill. He is sent to Bethesda Navy Hospital to their radiation unit (considered the last stop on the way to the cemetery, by those in the radiation industry).

Tony tries to help Ziva remember who the man is: they check all possible places where their paths could have crossed, but they have never been in the same place at the same time, according to the Lt's passport. Gibbs is suspicious of the man until they prove the guy innocent. Ziva is assigned to guard the man at the hospital and keep trying to recall where they met.

The rest of the team interview and surveil the other team members who were in Brazil with the man. The older guy and Lt Roy went to the pistol range together, so footage is pulled from the security cameras there. The owner, a woman of voluptuous appetites, scares Tony but a radiation check of the area finds no evidence against the place. Attention turns to the older inspector but, when interviewed, he too ends up ill.

Abby and Ducky do their science work. McGee had been required to be checked out because Lt Roy coughed on him. In an act of truly awesome Abby vindictiveness, dressed as sweet innocence, Abby cuts a serious hole in McGee's precious Armani jacket, having sworn she would not dirty it. On returning it, she sweetly says she didn't dirty it, she merely cut it. The patch missing is larger than McGee's hand. McGee has had to hang around in an office, naked, whilst Abby processes his clothes, until he borrows hospital scrubs from Ducky and goes back to the squad room in his medical outfit, prompting Tony to ask Ziva "What does McGee look like?" Ziva answers "A male nurse" to which Tony retorts, with a smirk, "Aqua smurf".

The big puzzle is how did the Lt Roy get poisoned? It appears it did not happen on the job, or the other inspectors would also be poisoned. So he was targeted. What did he eat? Nothing poisonous or others would be ill too. Turns out it was in his cigars. But they only work that out after Roy has been sneaking out of the hospital ward to the gardens to smoke and continue poisoning himself. We found out by further review of CCTV footage that the older investigator became slightly ill because Roy smoked a cigar after they had done their pistol range practice and the old guy inhaled the smoke. (This also showed that he did not poison the cigar, because he would know not to be around when Roy smoked them...). Indeed, the older guy was a good friend of Roy's, to the point of being a confidante.

Ziva and Roy's conversations have revealed, eventually, the solution to the "how do I know you?" puzzle: they realized that they saw each other each morning when jogging around the park. Roy did his run of 8 miles every day and, even when falling ill, only reduced his speed marginally. (A meter in his shoe recorded his running data.) Gibbs observes that the data tells him much about the man: that he would have made a good marine (which is a high compliment, as we know). She noticed him because he was so fast when he passed her. He confesses that he always put a little something extra in his pace in order to impress her and that he would look back at her to admire her technique - her nice, firm technique.

Ziva has been falling for the man more and more whilst he is in hospital, but she knows he is dying. The doctors could not work out how his radiation levels were going up instead of down. Eventually even Roy realises that he needs to make his Will (a service provided by Agent Lee, graduate of Harvard Law School and who kindly says she hopes that the Will will not have to be used for a very long time: elegantly put and one of the few times that Agent Lee is seen as a serious, rather than comic, character). He leaves his estate to his sister . He says that he would like Ziva to meet his family.

On inspecting Roy's desk, Tony had found a picture of a woman: he had warned Ziva of another woman in the man's life. Ziva followed up on Tony's interrogations and learns that the woman is Roy's sister. Tony and Ziva have a tragi-comic scene by the vending machine in the waiting area at the hospital: Tony swears at a recalcitrant vending machine so Ziva advises Tony on how to hit it to make it work. Tony observes that you know you have been in a place too long when you know how the candy machine works. They sit, side-by-side and have a heart-to-heart, Ziva identifying the "other woman" and Tony telling Ziva that there is no shame in falling for the dying guy. Ziva, angrily, asks what is she supposed to consider it? "Life-affirming?" Tony, at this point, is demonstrating the emotional maturity hard-won from the relationship with Jeanne.

However, once Tony finds out that Roy is not two-timing, he partially restores his madcap credibility and lends a hand in distracting the doctor so that Ziva and Roy get time alone in the garden to talk. Roy has interrupted the Tony-Ziva heart-to-heart by stumbling from his room to request a pretty girl to take him to the garden. The doctor chances upon them and orders him back to bed. Tony's distraction device is to bend over, moaning, groaning and calling for the doctor's help..he pretends that he has radiation sickness: the doctor falls for it hook, line and sinker, forgets Roy and starts asking questions about bowel movements which Tony answers (wow, he really is a good friend to Ziva). Ziva and Roy, watching in appreciative amusement, sneak away....

The investigation continues and our suspicion is directed at the female co-investigator. She knows where the next inspection will take place. That next-to-be-inspected nuclear facility is in the former soviet union: it has a vested interest in not letting Roy (who has done previous inspections there) seeing what has changed (for they are being Naughty (nuclear naughtiness deserves a Capital N, by the way). McGee tracks down bank payments to "her" and thus McGee and Gibbs race off to the IAEA offices, to find female investigator booking a plane trip to Europe. But they ask "where did she go?" and, after some frustrating, wrath-inducing stalling by the disgruntled investigator, they race to the car park to arrest...the secretary who does the travel arrangements for the trips (and thus knows where the inspections will be and can be bribed to interfere with them...). She just wanted Roy to not go on the next mission, so she put something in his cigars of the radioactive, deadly kind.

How did they find out it was her? After Roy fell ill, the entire office was required to be tested to see if they were ill. Gibbs had Ducky get those test results and look them over. The secretary, Holly, was the only person who had been taking the prophylactic medication to prevent being affected by the radioactive substance that she put in the cigars. Ducky spotted it after prompting from Gibbs to check for it....(they are SUCH a dynamic duo, that Batman and Ducky)

How did they catch her? Well, McGee and Gibbs were too late to stop her getting in the car and driving towards the exit of the office car park, but they weren't too late for Gibbs to race to the exit and be standing in front of the car, pointing a gun at the driver as she sped towards him. And he won the bluff: she stopped. And blabbed that she didn't mean to hurt anyone, etc etc as she is hauled from the car by McGee. Holly says she only meant to make Roy sick and is informed by the Gibbs stare that her actions have killed Roy. And, whilst handcuffing her, McGee rebukes Gibbs, saying that "she could have killed you, Boss" in an admonitory tone (i.e., McGee's heart was in his mouth as he watched the car heading towards Gibbs and Gibbs not moving). Gibbs just lets the rebuke slide past him.

So before Roy dies, Roy knows who his murderer is (ah, what a comfort that must be). But that is too late for him: the radiation has had its effect (and it is a brilliant warning against the evils of smoking cigars, although perhaps disproportionate in the punishment). Roy asks whether Ziva would have noticed that he wasn't running anymore. She says she thinks she would: she would miss his smile. (and the fluro orange beanie that he wore while running, which he fetchingly had to wear for the final scene, in the beautiful, green and quiet garden of the radiation unit...an Eden for the dying, complete with still water pond, and lovers' bench for sad farewell scenes in a gentle, fading, golden twilight sunshine...). Roy says that she would have forgotten him. Ziva says she would have but she will never forget him now. And puts her small hand inside his big hand, and that is the final shot: their hands intertwined.