Na vojenskou základnu ve Virginii zavolá anonym a oznámí vraždu muže. Jde o důstojníka Thomase Egana, případu se ujímá Námořní vyšetřovací úřad. Oběť působila jako technický poradce a civilní dodavatel pro základnu. Podle výpovědí kolegů odešel Egan brzy ráno provést testy jednoho jejich podvodního zařízení. Měl u sebe speciální ruční zbraò, která využívá ozvěny zvuků na vytvoření vizuálních obrazů - jako sonogram. Jejich novou verzi však unese i potápěč. Vynalezli tento koncept a předali jeho jediný prototyp armádě. Egan byl odborník na radarové ozvěny a přístroj testoval.

NCIS zjistí, že anonymní hovor byl z budovy CIA. Gibbs navštíví šéfa CIA a žádá ho o spolupráci, protože někdo z jeho lidí je podezřelý ze satelitní špionáže americké základny. Žádá o nahrávky satelitních přenosů, ovšem neúspěšně. Gibbs však ví jak obejít "úředního šimla" a požádá Abby, aby zatelefonovala svému dávnému příteli z NASA, který má na starosti kontrolu vojenských satelitů a neoficiální cestou ho požádala o zjištění, který satelit se v inkriminované době nacházel nad místem zločinu a kdo ze CIA jej obsluhoval. Poté co Gibbs, takto nestandardně, zjistí dotyčnou osobu - mladého technika Wortha, tak ho spolu s Kate vyslechne a přinutí mluvit. Zjistí, že nešlo o špionáž americké základny, ale Worth pouze obešel interní předpisy CIA a sledoval z vojenského satelitu nahou ženu opalující se na pláži. Při té příležitosti se mimo jiné stal svědkem vraždy a byl to právě on, kdo telefonoval na vojenskou základnu. Gibbs zatelefonuje řediteli CIA a opět žádá o spolupráci, jinak vše zveřejní. Dotyčné záběry získává, ale vraha se mu přesto nepodaří identifikovat.

Jeho tým se tedy zaměří na hledání oné tajemné a neznámé nahé ženy ze záběrů. Jedná se o zaměstnankyni vojenské základny Ginu. Ta sice z dálky viděla nějakou hádku, ale odešla z pláže dříve, než k vraždě došlo. Jediným vodítkem pro Gibbse je to, že Gina si je jistá tím, že s Eganem na místě činu byla žena a hodně nahlas se spolu hádali.

Podezřelými se stávají Eganova nadřízená Lauren Tylerová a trochu překvapivě jeho manželka. První je podezřelá, protože měla s mrtvým intimní poměr a druhá z toho, že na to pravděpodobně přišla a manžela zabila. Gibbs nastraží na Eganovu manželku past tím, že jí sdělí, že Eganova nadřízená je podezřelá z vraždy a prvořadým úkolem vyšetřovatelů je nalézt ztracenou ruční zbraò, která by Lauren usvědčila. Past zabere a Eganovu manželku usvědčí. Gibbs jí se svým týmem přichytí přímo při tom, když si dojede na tajné místo pro dotyčnou ruční zbraò.

Tony enters from the elevator, munching on a doughnut. He offers one to Kate, who refuses, saying she likes keeping her belt notched exactly where it is. (She also sounds a little hoarse; Caitlin seems to have a cold.) There is brief discussion of Tony's weight, about which he seems to be a wee bit sensitive. Gibbs comes in during this conversation and smirks a little bit (which is very nice), then gets a call. We watch Tony tighten his belt to the point that he can't breathe. Gibbs hangs up and announces a murder at Little Creek. Red-faced from the lack of air, Tony follows Gibbs out as Kate, calling Ducky, grins at him. Kate's got a great smile.

The team is approaching the body across a familiar stretch of beach. A fellow in fatigues tells Gibbs that he located the body after an anonymous tip was called in to base security. The victim has been identified as Lt.Cmdr. Thomas Egan. As they approach the body, Tony points out that the body has not been robbed; he is still wearing an expensive Tag Heuer watch. Kate begins taking crime scene photos. The fellow in fatigues reports to Gibbs that Egan was attached as a technical adviser to SideScan, a civilian contractor on the base. He knows nothing else as the SideScan work is classified.

Things get busy when Ducky realizes the tide is rising; the body must be kept dry in order to preserve evidence. Everyone kicks it into high gear. Gibbs and Tony begin taking measurements as quickly as possible; Kate takes more photographs. Measurements are taken; Kate notes that Egan's dive knife is missing. A wave comes up; Tony self-sacrificially tosses himself between the very cold water and the body, successfully keeping the body mostly dry but soaking himself in the process. Did we mention it's January in Virginia? Brr.

At the SideScan offices, Egan's co-workers are shocked and appalled to learn that he is dead. They last saw him early that morning as he was heading out to do some underwater tests on a piece of equipment. The man (Overmeier) asks if they found a device with Egan's body. Turns out, Egan was working on a hand held sonar gun. Overmeier's company developed the gun; Egan and the woman (Cmdr. Tyler) were evaluating it. Gibbs seizes Egan's computer and anything else he thinks they might need. This does not make Tyler or Overmeier happy.

At the Little Creek Quarterdeck, Tony (dressed fashionably in Ducky's spare jumpsuit which is at least two sizes too small and several inches too short - why hasn't his voice gone up an octave?) is obtaining the information about where the anonymous tip came from. The call came in at 09:32, no name, but the voice was male and nervous. The caller ID on the call was blocked. Tony goes to McGee, who hacks the database to find out who made the phone call. While McGee works, we learn that he is still seeing Abby occasionally. McGee locates the number; for some reason there is an asterisk after it. Tony tells him to find out why.

Kate and Gibbs go to Egan's house to interview his wife. Gibbs can't read the small print on Kate's PDA. Lieutenant (Mrs.) Egan answers the door, looking all sad and crying. Lt. Egan states that she was gone all weekend to Camp Lejeune for a seminar; when she arrived home, the notification detail was at her house to tell her that her husband was dead. She last spoke to her husband around 10pm the previous night, and was unaware that he was going diving that morning. However, as a SEAL, it was not unusual for him to go diving many times in the week. She also did not know what his project was; the Lt. Cmdr. was very strict about classified information.

In Autopsy, Gerald is going to open the body bag when it moves. He jumps back. Ducky is exasperated with him until he, too, sees the body bag move. They open it carefully; a crab jumps out.

Kate and Gibbs park out on a strip of asphalt somewhere. They discuss the possibility that Egan's death is espionage. Tony arrives and shares that the anonymous tip came from a restricted phone in Langley, VA; which leads Gibbs to believe it's the CIA.

Back at HQ, Kate enters with a computer tower. Tony, dressed again in his own clothing (thank God), is eating a "nutrition" bar. Kate mocks him for it, pointing out that it's not nearly as healthy as he thinks it is. She reads the ingredients, which make us all want a banana, and Abby arrives for Egan's computer. Abby asks after Gibbs but he is in with Director Morrow, trying to get a meeting with the CIA to find out about the anonymous tip. Time of death was established as 09:30, the tip came in at 9:32, and Langley is over 200 miles from Little Creek. Abby points out that this is impossible; Gibbs, who has arrived to retrieve his coat, rebuts that it's not impossible if someone from the CIA was watching on a high-definition satellite.

Gibbs meets privately with someone from the CIA (Roper), who insists that this could not have happened. Gibbs points out everything he has - dead Egan, missing classified prototype, and anonymous phone call originating from the CIA building. Roper does not deny the capability, but points out that domestic spying, such as what this points to, is illegal. Gibbs points out that they both work for the same government, and politely (for Gibbs) asks for Roper's help. Roper refuses. Gibbs takes another route - Abby has a boytoy who works at NASA and can help them track down their satellite user. Great insight into Abby's deeply playful nature. Ashton locates the building and office from which the satellite was controlled that saw the murder.

That evening, Kate and Gibbs wait on the street in front of the building where the young satellite controller (Worth) lives, waiting for him to come home. There is slightly flirty banter that makes the shippers sigh. Kate has a great laugh. Worth arrives home; they approach. Worth doesn't want to talk; he's on administrative leave and under investigation for his unauthorized activities with the satellite. Gibbs offers to go to bat for Worth if Worth tells him what he saw. Worth admits he was watching the nude sunbather when the murder took place and couldn't see the murderer. He tells Gibbs that all satellite transmissions are recorded on a hard drive at Langley; if he could access his computer, he could show Gibbs exactly what he saw. Gibbs gets on the phone with Roper and threatens to have Worth talk to a Congressional oversight committee if Roper doesn't let them see the satellite shots.

In Autopsy, Ducky determines cause of death to have been that Egan was stabbed with his own dive knife, and judging by the angle of the thrust, the assailant was probably left-handed. Abby is working on Egan's computer; it was password-protected and took some time to get in. Tony, Gibbs and Kate arrive to find out what she has. Gibbs has brought a copy of the satellite shots for Abby to enhance. Abby reports that Egan's notes indicate he was hinky about the reliability of the sonar device. On the beach, divers are searching for the sonar device.

Abby is unable to clear the picture up enough to make an ID. Tony suggests looking for Polar Tanning Girl instead; perhaps she saw something. Abby prints him a picture of the girl's face. Kate is to stay with Abby and go over Egan's files to learn about the device. Ducky comes to tell Gibbs about the assailant being left-handed. Ducky also found traces of a female's DNA on Egan's body - meaning that Egan was probably having an affair with someone, since his wife was gone all weekend. Gibbs goes back to the Egans' home to question Egan's wife. He asks questions about SideScan and Egan's project. He asks about how much time Egan spent at work; indications are that Lt. (Mrs.) Egan seems to know about the affair. She checks her watch and we note that she wears it on her right wrist, as a left-handed person might.

In the Little Creek Base Gym, Tony watches women work out. (Typical Tony.) He shows the photo to the gym manager, who says that it could be Gina, who comes in every day around noon. Since it is 11:40, Tony decides to wait. Also typical of Tony, he has to play with the equipment while he does so. Gibbs meets with Cmdr. Tyler privately to inquire about the device. Tyler admits Egan did not think the sonar gun's range was as good as promised; if he turned out to be correct, the Navy would not purchase the gun from SideScan and Overmeier would lose a lot of money. If the prototype is not found, SideScan would get an extension, giving them time to correct the flaws. He tosses out the suspicion of Egan's affair; Tyler admits she and Egan have been seeing one another for months. She, too, checks her watch; she wears it on the left wrist, as a right-handed person would. (Some lefties also wear their watches on their left-wrists as well.)

By the time Gina gets to the gym, Tony is out of his shirt and jacket and just in his undershirt, so when he approaches her, she thinks he's hitting on her and blows him off. Tony gets his ID and comes back, opening the interview. At SideScan, Kate and Gibbs are pretty much cleaning out the office and all the files. Gibbs confronts Overmeier about his suspicions; Overmeier is blustery and full of himself. Gibbs points out that Egan's death buys Overmeier time; Overmeier blusters some more. Gibbs has Overmeier sign a receipt for his files; we see that Overmeier is left-handed. Outside, Gibbs and Kate discuss Overmeier's left-handedness, and Kate points out that he and Tyler could be in it together. Gibbs says they could in a way that indicates he doesn't think they are. He gets a call from Tony reporting that Gina is in fact the polar tanner. Gina reports that she thought Egan was alone at first, but when she glanced back, she saw him arguing with a woman who was definitely military.

Returning to HQ, we get the rundown from Kate and Tony. Egan's killer was a woman (eliminating Overmeier) and left-handed (eliminating Tyler). Gibbs points out that perhaps they followed the missing prototype too hard; it's possible the murder had nothing to do with that. They begin to examine Lt. (Mrs.) Egan instead, who had a motive as she knew her husband was having an affair. Kate points out that Lt. (Mrs.) Egan has an alibi. Gibbs points out that she plays golf left-handed; he saw the clubs. They go back to the house to question her again.

Gibbs has an unusual method of questioning. He tells Lt. (Mrs.) Egan that he thinks Egan was killed over flaws in the SideScan sonar prototype thing. He and Kate further state that they need the prototype to build a case against Lauren Tyler. Kate asks about the affair; Lt. (Mrs.) Egan pretends to be all surprised. She continues to insist that he never talked to her about the project. She asks why they think Egan was killed. Gibbs straight-up lies; he tells her that he thinks Overmeier bribed Egan and Tyler to keep quiet about the sonar gun's flaws, and that Tyler killed Egan when Egan refused the bribe. He stresses the need to find the prototype as conclusive proof that Tyler was involved in the murder.

Outside, Kate and Gibbs discuss their little play-act. Gibbs thinks Lt. (Mrs.) Egan took the bait. Kate hopes they are right, because her bleeding heart would feel bad if they put an innocent woman through that. Gibbs calls Abby and has her get back in touch with Ashton for some more surveillance.

There is discussion in MTAC - Ashton admits to Abby that the satellite he is using is technically down for maintenance. They are watching the Egans' home. Lt. (Mrs.) Egan leaves in a big hurry. Abby redirects the satellite feed to the computer in the car where Kate, Tony and Gibbs are waiting. They get some separation and then head out in pursuit. Lt. (Mrs.) Egan leaves the base and heads south. Gibbs follows. In the midst of pursuit, the satellite signal is lost; turns out the satellite was down for maintenance for a reason. Ashton gets it back a few moments later and she is re-located driving into the woods.

We watch her get out of her car and hurry over to a place marked with some rocks. Pushing the rocks aside, she pulls out the sonar gun and the bloody dive knife. Gibbs' voice offers her a hand, and she gasps, turning: standing above her on a slight ridge like Charlie's Angels are our Intrepid Team, catching her in the act.

Back at HQ Tony comes in with Ducky's spare jumpsuit in a dry-cleaner's bag. He is late because he had to go pick it up. Gibbs is not pleased; turns out Tony's phone has been ringing off the hook. Gina apparently decided Tony was cute after all and has been calling nonstop. Tony's not interested; she's not attractive enough for him. Tony's version of letting her down easy is just not answering her calls. Gibbs warns him to handle the situation. There is banter regarding Gibbs getting whacked on the head with a golf club, and Gibbs has a great smile.