Při pohřbu námořníka vybuchne v kostele krypta s kosterními ostatky. Pyrotechnici neobjeví žádnou bombu. Doktor Mallard proto má vysvětlení. Jedná se tzv. Syndrom vybuchnuté rakve. Pokud se v uzavřeném prostoru rozkládá lidské tělo a vypouští plyny stanou se tyto samotnou bombou. Někdo věděl, jak se krypty otevírají a že zrovna v této kryptě bylo dost místa. Mallard zjistí, že v kryptě bylo přinejmenším 5 koster lidí. Má podezření, že se jedná o masového vraha.

Abby zjistí z fotografií kostelní kryptové haly, že ještě pouze dvě krypty mají nerezavé a opotřebené šrouby a tudíž mohly také sloužit jako místa úschov mrtvol. V jedné z nich objeví Gibbs další kostry. Několik kosterních pozůstatků je identifikováno. Prvním podezřelým je Len Grady. Vyšetřovatelé zjistí, že u všech identifikovaných prováděl čištění bazénu. Při výslechu však nic nepřizná. Další vyšetřování zavede Gibbse a jeho tým do řeznictví, které patří Natalii Daltonové - jejíž zemřelý otec měl v kostele kryptu, ve které se našli kosterní pozůstatky a navíc znala Gradyho. Najdou v jejím obchodě zbytky lidské krve.

Když je Natalie na výslechu, mají vyšetřovatelé v odposlechové místnosti Gradyho. Ten se pod tíhou odpovědnosti a z důvodu ochrany Natalie přizná ke všem vraždám. Natalie ve výslechové místnosti vše slyší. Gibbs Natalii propustí a jde hledat Gradyho dodávku. Má však něco za lubem a jeho podezření se potvrdí. Najde dodávku a při jejím otevření uvnitř nalezne Natalii, jak porcuje další mrtvé tělo člověka, kterého Grady usmrtil.

Two men are trying to open a vault as a funeral is taking place outside. The body from the funeral is to be placed inside the family crypt. When the first man is unable to get it open, the second man tries. As the vault screws loosen, the first man smells something funny and then the vault explodes throwing both men backwards with a lot of "goo" flying all over. The second man looks up to see multiple skeletons, two skulls and lots of "goo" all around.

Abby shows up in the squad room begging McGee for a dollar. She's upset the candy bar she got has nougat in it. She hates it as McGee points out. Uptight, Abby tells him she knows that's why she needs a dollar because the machine won't accept the one she has. Ziva asks what nougat is and Tony tries to explain but Abby freaks out on all three of them prompting Tony to give Abby a dollar. Abby walks away with his dollar, forgetting to give him hers in return. McGee is concerned about Abby as she wasn't herself. Tony says he will talk to her which sparks a conversation between the two men about "sensitivity." Ziva inquires again, what nougat is and Gibbs walks in, gives her an explanation and then tells them they gotta roll.

Gibbs and his team arrive at the cemetery. Tony jokes about being the last for the party but is reminded that they have to wait for the all-clear from the bomb squad. Gibbs meets the head of the bomb disposal squad and is informed they found no evidence whatsoever of a bomb. The two men from the cemetery had been brought to the hospital with shrapnel wounds and concussion from the explosion. Before the NCIS team enter, the bomb disposal squad warn them to cover their shoes as theirs are covered in "goo" and they might want to wear masks because of the odor.

Gibbs and the team enter and despite the horrendous odor, start checking out the crime scene. They notice all the skeletal remains (which were not in a coffin) and inquire where the bodies were. Ducky and Palmer show up at that moment and Ducky points to the "goo" and tells them that, that is the remains of the body itself. When a body is left in the open, it immediately disintegrates and with no ventilation (the vents were blocked), it formed a gas, which caused the explosion. Palmer is sent to retrieve a shop vac to suck up the "goo" for evidence.

Upon returning to NCIS, Ducky and Palmer sort through the skeletal remains. They find two bodies, that of a man and a woman. Upon separating the parts to complete one victim's body, they discover a third right hand and realize there is another body. When Gibbs visits autopsy, Ducky points out the two bodies, which are incomplete due to missing bones. Ducky shows him that the bodies were skilfully cut up and dismembered. He then shows Gibbs a table with extra bones belonging to not one but several more victims. They realize that there are probably more bodies in empty vaults.

Ziva and McGee meet the first victim's family, a 58 year old woman who had not been reported missing, Mrs. Torrance. They meet the nephew and his wife. The Aunt tends to go off with someone and disappear for months and only stays with them when she's in town, the nephew reports. They were unaware she was missing because she is in the habit of not communicating with them while she is away. As the woman cries, Ziva gets a look from McGee, as she hands the woman a box of tissues and consoles her.

Tony is set to meet another woman, Natalie Dalton, to obtain permission to open her grandfather's vault. Her grandfather is the only body in there and he's been dead for 13 years, Natalie tells Tony. Tony manages to blunder the simple job when the woman wants a lawyer to review the paperwork. Tony mentions if she doesn't sign it then they will have to get a warrant. She tells him that she owns her own business and loses money the longer he delays her. Natalie grabs her purse and thanks him for saving her time and tells him to get the warrant. She leaves Tony behind as he realizes what he's done.

The team now has the warrant to open the Dalton family vault so they arrive, warrant in hand, to open the Dalton vault. When they arrive, they find Lt. Col. Hollis Mann and crew waiting for them. Mann was alerted when NCIS had to get the warrant so she arrived in case it was an issue involving her. Gibbs and Mann both look uncomfortable as they hadn't talked since they slept together at the end of "Sharif Returns" 6 weeks earlier (episode 4.13). The Mann/Gibbs reunion starts out in front of Tony and Ziva: they are agog to see Gibbs uncomfortable and not in control of a situation. Mann puts Gibbs in his place. Gibbs orders them to maintain the perimeter of the crime scene, to give him and Mann privacy. Their argument over who was meant to phone whom is a classic in doublespeak. Gibbs finally says that he didn't think they wouldn't talk afterwards and she says the same. Both were too stubborn to pick up the phone and call the other. While cooling their heels outside, McGee, Tony and Ziva stop a young man from going inside. He is bringing lilies to his mother's vault he tells them, but they turn him away.

When they open the Dalton vault, they discover more skeletons and "goo" inside. They return to NCIS and Ducky shows them 5 bodies; each killed in a different way - shooting, stabbing, blunt force trauma to the head and so on. None of the victims had anything in common. They ranged from a 70 year old woman to a 19 year old runaway; male, female, white, African-American and Asian. There is nothing the 5 victims had in common. As they are chatting, Director Shepard calls down and asks Gibbs and Mann to report to her office.

Director Shepard informs Gibbs and Mann that Mann is on loan to NCIS until her services are no longer needed or the case is closed. She asks if they have a problem with that. Mann doesn't as long as Gibbs is forthcoming with information. Gibbs doesn't as long as Mann realizes he is in charge. Shepard comments how well they worked together before and asks if anything has happened to change that. Both of them just look at her and it prompts Shepard to dismiss Gibbs and ask Mann to stay behind for a private chat. Gibbs leaves and Shepard offers Mann a drink of bourbon. Mann jokes that somewhere the sun is already set when Shepard asks if it's too early to drink. Shepard tells Mann that bourbon is an acquired taste, just like Gibbs, one you never get over. The two women have a conversation about Gibbs, which we are not privy to.

They are able to identify all of the remains for the five victims. They realize all but one of them had been reported missing, Mrs. Torrance. They pull up information on the family of the victims and the Giblets see Len Grady's photo on the big screen. They recognize him from his visit to the cemetery when they were there. They pull up a website for Len, advertising his rather versatile career. He is a jack of all trades; plumbing, landscaping, carpentry, pool cleaning, etc. Pool cleaning triggers something as Tony had just learned that traces of bleach used to clean pools was found on the victims. The 78 year old woman that was found dead had Grady cleaning her pool on a regular basis. Gibbs tells them to go pick him up.

When Tony and Gibbs are staking out Len's house, Tony reports the neighbors saw Len leave an hour prior to their arrival. They sit and wait but ever curious, Tony comments about Shepard and Mann. Gibbs tells him they will wait in silence. Shortly after they see Len walking up, which begins a foot chase. As Len rounds the corner of his house, Ziva sticks her leg out from behind a tree and trips Len. McGee tackles him and puts him in cuffs. Gibbs returns to NCIS with Len while the Giblets go through Len's house. They find knives, saws, etc. in his house and bag them and return them to Abby. They also find a package of meat in his freezer, using the same type of rope they found with the victims. They open it to find a pork chop, which they also bring to Abby. They team is unable to find Len's van and put out an APB on it.

Back at NCIS, Tony makes an attempt to talk to Abby, to get her to open up. It backfires as Abby accuses him of gossiping and talking about her behind her back. It appears to make Abby angrier so Tony leaves. Ziva also tries to talk to Abby but Abby only talks about her shoes, why she wears them, etc. In the squadroom, Tony says he talked to Abby. When a concerned McGee asks what is wrong, Tony blames it on McGee. Ziva says Abby is upset about her shoes.

The team is discussing the case when Abby calls them down. Tony tells Gibbs Abby isn't herself and Gibbs says he's not going without something in hand. Gibbs shows up with a CAF-Pow for Abby with Mann and Tony trailing behind. Abby tells them that all the knives, etc. they found in Len Grady's house do not match the incisions/cuts made on all the victims. She picks up the pork chop, which Gibbs hands over to Mann and says that the cuts made on the pork chop DO match those on the victims. She tells them that whoever cut the pig is responsible for cutting up the victims. Mann and Tony leave to do searches for butcher shops. Gibbs remains behind and looks at Abby. She tells him he doesn't have time and Gibbs tells her twice, he has time. He walks with her to her desk and she tells him she was dating a man but he ended it because she was "too much" for him. She's upset about it and vents, staring at the guy's picture on her computer screen. She finally deletes the photo and thanks Gibbs for knowing what to say to make her feel better (he never said a word, just listened). (They wrote off Abby's boyfriend as the actor who portrayed him died in real life.)

Gibbs meets Mann in the hallway to interrogate Len Grady. He comments about her perfume and she says she isn't wearing any (it's the bourbon he smelled). Gibbs and Ziva interrogate Len Grady. He doesn't admit to anything but Mann notices he looks relieved as Gibbs lays out the photos of the victims in front of him. When Gibbs leaves the interrogation room and joins Mann in observation, she tells him Len's not the monster, someone else is.

Ziva goes to Abby's lab and notices Abby's music is playing again. She's happy to see Abby is feeling better. Abby says it's thank to Gibbs. She tells Ziva that she and Gibbs had a good chat and it made her feel better. Abby tells Ziva if she wants to talk about roy Sanders, Abby is there to listen. Ziva says Roy was sick, she liked him, he died, end of story. Ziva tells Abby that she is glad she's feeling better one more time and leaves

The team does a search and they narrow it down to one butcher shop. When the team arrives at the shop, the owner is none other than Natalie Dalton. Natalie admits that Len Grady is her boyfriend. As they search her shop, they find a locked freezer. Natalie says she uses it for overflow during the holidays and hands Gibbs the key. When Gibbs opens it, they find blood inside.

At NCIS, they interrogate Natalie while Len watches, crying in observation. Natalie lays all the blame on Len, claiming she didn't know what he was up to. She says how he was interested in what she was doing and she taught him how to use her tools, etc. and he had access to her home, shop, freezer, etc. She cries as she is upset to learn of what he is doing. On the other side, Len confesses and says he did it and tells them exactly how each one was murdered. He bangs his head on the double-sided mirror, crying and yelling to Natalie that he loves her and he's sorry. Natalie slightly hears him but Len is removed from observation. Gibbs lets Natalie leave.

Later, Gibbs is driving with Mann talking about the case. She mentions how he is always right and so on. He pulls into a parking lot and parks. They both get out and approach what turns out to be Len's missing van. Both of them hear a noise inside and pull out their weapons. Gibbs opens the back of the van to reveal Natalie dismembering victim #6. The scene ends with Mann saying "son of a..."