A dying woman drives her car into a diner, barely missing a couple of young people dealing with a failed marriage proposal.
The victim is Navy Ensign Janine Wilt, who is 25 years old. Her throat was slit.
Tony finds a t-shirt in her car with a high school emblem on it.
Gibbs and Bishop visit the high school and speak with Coach Ruth Curry. She tells them Wilt worked as a volunteer coach for the basketball team. She mentions that Wilt's job involved computers.
McGee tells Gibbs that Wilt worked as a cyber warfare engineer with Naval Intelligence.
Navy Captain Chester Berk briefs Gibbs and Vance about the work Ensign Wilt was working on before her death. She was involved in targeting a group called "Sword of Satan". Ensign Wilt had hacked the Columbian drug lords' dark web server and deciphered their communications.
Special Agent Ned Dorneget is assigned the task of breaching the security of Wilt's laptop.
Captain Berk sends McGee some intel on the operation Berk was operating on.
Tony and Bishop capture one of the targets of Wilt's operation, Alfredo Montez. He believes they're there to kill him and is surprised when they merely apprehend him.
Bishop and Tony question Alfredo, who tells them about the communications network he had set up that was compromised by Wilt. They find out that Alfredo doesn't know who hacked his server, and is therefore not Wilt's murderer.
Ned tells Gibbs that Wilt gained access to Adem Faruk Korkmaz's home computer two nights ago.
Bishop and McGee question him at his home but he denies knowing Wilt and assures them no one hacked his computer.
Vance informs the team that the NSA holds a FISA warrant to monitor Korkmaz's computer. He tells them to stand down.
Bishop demands that Jake tell her what dealings the NSA has with Korkmaz but he refuses, telling her that it's classified information.
She confesses to him that she killed a man in Kabul last week, and that she's trying to deal with it.
The next morning, Jake surrenders access jurisdiction on Korkmaz's computer to Gibbs and hands him a Solid State Drive (SSD) containing all the data they've taken from the computer.
Ned pulls up a file from the SSD containing names from a chat room.
Bishop enters the interrogation room with a file folder. Korkmaz breaks and confesses to selling knock-off designer bags. He believes that's why NCIS nabbed him and his computer.
Bishop shows him the chat room list. He recognizes his daughter Layna's chat room screen name. Korkmaz tells them she's forbidden from using his computer, but then realizes she has done so anyway.
They bring Layna in for questioning. She tells them her school doesn't allow any students personal email or social media access, and this is why she has used her father's computer.
Layna tells them she was lured to one chat room in particular. She says it was creepy, and filled with discontented haters. The participants asked her if she was lonely, and if she knew her "calling".
She says she quit the chat rooms, but then found herself the recipient of strange messages. She says they tried to shame her into coming back, saying that she needed them, and that her life was nothing without a purpose.
She says she turned to Ensign Wilt who promised to help her and to not tell her father. She says Wilt remotely access the computer in the middle of the night, deleted the email account and blocked all access to the chatroom and everyone on it.
Layna identified a few of the screen names, and in particular her stalker, with the screen name of "hellbent427".
Abby tells Gibbs that the weapon used to kill Wilt was an old bayonet used in Vietnam.
Ned discovers that the name "hellbent427" is sixteen year-old boy by the name of Bradley Simek.
Tony and McGee go to Simek's house. While there, they notice Simek's father's bayonet collection. There's one missing from the display.
Tony, McGee and Mrs. Simek go up to Brad's room only to find that he's gone and the window is wide open.
They hear the garage door opening. Tony and McGee rush down the stairs, only to find Brad escaping in the family SUV.
They bring Brad's computer back to NCIS for examination.
Ducky provides a profile of Brad Simek to Gibbs, identifying him as a malcontented teen who only bonds with similar malcontents. Gibbs theorizes that this could include a terrorist group.
Ducky theorizes that Simek killed Wilt in order to prove himself to the mastermind of the group in which he participates.
Abby discovers that Brad's computer has traces of gunpowder. Ned and Abby discover a 3D printer blueprint for a bomb detonator.
McGee discovers Brad's cell phone signal. Brad calls his mother but doesn't say anything.
The team follows Brad's cell phone signal, and realize he's likely on a bus. They signal the bus driver to pull over.
Gibbs gets on the bus and orders everyone off. Brad stands up, holding the detonator. He tells everyone to stay where they are.
Gibbs points his gun at Brad, while quietly telling the passengers to escape.
Brad tells Gibbs that the knife used to kill Hilt was his but that he didn't murder her.
Gibbs tells Brad to follow him out off the bus.
Gibbs gets off the bus. Brad is about to get off, but he hears a police siren. He changes his mind and runs to the back of the bus and detonates the bomb.