Episode Summary: When an antiterrorism device is stolen, the team must quickly find the suspect and the device before an attack is made against Los Angeles. Meanwhile, Hetty realizes the case is bringing her back to someone from her past.
A security guard locks up an office for the night. A man enters through the ceiling using a rope. He turns on a computer at one of the desks and copes data onto a hard drive. He exits the building down a fire escape ladder and gets a ride from someone on a motorcycle. A masked man walks up and starts shooting at them. The motorcycle crashes and the security guard takes the masked man down. He turns towards the man near the motorcycle but is shot by the man lying on the ground behind him who was wearing a bullet proof vest. One person gets away on a motorcycle but the man wearing the vest retrieves the hard drive.
Hanna discusses money with Callen after he spent a month building cabinets. Everyone suggests that he should have hired someone so that he could relax doing whatever he wants. Marty agrees with Callen's preference to hire a professional. Kensi says that a man who can build things for himself is sexy. Eric calls the team up using a morse code text message.
The team arrives and Eric tells them about a robbery and shooting. The security guard shot, retired Marine Gunnery Sergeant Dennis Martin, is currently in surgery. The thieves stole files that reveal the location of devices that can locate and detect sources of nuclear radiation. The devices are used to prevent terrorists from bringing nuclear bombs into the country. Hetty calls and asks that Nell send a copy of the files to her. The dead thief, Brody Stallworth, has a long list of robberies but they haven't discovered the identity of the other man. The guy who got away on the motorcycle took a bullet and is probably looking for a hospital.
Hanna and Callen break into Brody's house and find a workshop that has custom tools for their jobs. Callen doesn't understand why these burglars broke into the Department of Energy, it's not your typical break and enter. Hanna finds a garage door opener. They go outside to courtyard with multiple garages and push the button. They head inside and find the motorcycle driver that was shot. In the surveillance video he was shot once but he now has three wounds. They believe that the shooter followed him back here to finish the job. They spot a security camera and hope that it can identify the man or his vehicle.
Deeks and Kensi visit the Department of Energy where the robbery took place. The supervisor, Laura Baker, says that the computer was accessed normally and the workstation belongs to Roy Kessler. He didn't show up for work that day and Eric says he is catching a flight in twenty minutes.
Callen and Hanna question Roy about his trip and his connection to the robbery. Roy says it looks bad but he claims to have been drugged last night by two girls he was partying with. When he woke up his pass key was gone. Callen asks why he was going to run away rather than help the investigation. Roy logged into the system and panicked when he saw what had been stolen. The thieves only copied part of the database, Los Angeles County. He warns that everyone is in danger.
Nell shows the team the image of the man wearing the ski mask that was seen outside the garage. He was also spotted nearby using a payphone with his ski mask off. They have no identity yet though. Eric says Martin is out of surgery and conscious.
Hanna and Callen meet with Martin, who isn't sure he will walk again. He asks for his phone and shows them a photo he took of the shooter driving away. The license plate can be seen in the photo.
Granger talks to Hetty about pulling the Griffin file. He asks if she thinks that Griffin's behind the bomb plot but she hopes he isn't. They couldn't prove anything years ago but Granger still blames Hetty for letting him go. He states that if Griffin is behind the attack, everyone will blame Hetty, ending her career.
Callen and Hanna show up where the car driven by the shooter was last seen. Kensi and Deeks are on their way but Callen and Hanna head in. Inside they find a blank sheet with many pins all over it. Deeks and Kensi arrive and help search for any clues. Callen finds a sheet that shows routing information for Cobalt-60, which is something used to make a dirty bomb. That would be worse than a nuclear weapon and Callen says this is all about psychological harm. The weapon will be used o disrupt everything. The pins may represent every possible location but there are too many to search quickly. Hanna worries that they may already be out of time.
Hetty tells Nell to find Griffin. She hopes that he isn't involved in the case and says finding Griffin is priority one. She asks Nell to be private about the matter.
Eric shows up at the warehouse and shows Callen and Hanna that he found the shooter's identity. The man is Farat Hadad, a member of the Syrian Special Forces. Eric can't make any sense of the pins on the sheet but he receives a message that the department had an alert to a possible radiation detection. Callen says they can't leave Eric alone but Hetty shows up with a shotgun to protect him.
Callen, Hanna, Deeks and Kensi head to where the alert was. The don't immediately see anything and wonder if it's just a set up. Callen spots a man in a jacket and realizes it's Hadad. They follow him and pull their guns on him. He panics and grabs a woman as a hostage. Hanna shoots him and Kensi brings the woman to safety. Callen searches Hadad but there's no bomb.
Granger meets Callen at the scene and asks why he didn't take Hadad alive. He asks for Hetty's location and tells him there's nothing he should worry about. Hanna shows Callen a note and photo of a man found in the magazine that Hadad was holding. He believes that Hadad was going to take that man out. Callen runs a detector over Hadad in search of Cobalt-60. He finds a weak but positive signal on his clothes. Callen receives an ID on the man in the photo, it's Richard Towzen. A man that is still in Ohio. Callen believes that the alarm set off her today was just a test to see the reaction to the radiation alarm going off. Kensi says that if he has radioactive material to waste on a test there must be even more out there.
Hetty encourages Eric to continue working at solving the pins. She suggests that he ask Nell for help. Eric asks Hetty why she is here and what's going on. She explains that it's possible that the man who is behind this may be a man that slipped through her fingers. She finds a hidden button behind some books. A projector turns on that overlays a map over the pins. The pins are meant to represent vulnerable targets from San Diego to Seattle. The red flags indicate targets that are in a one mile radius of downtown Los Angeles.
The team gathers around the map of targets and say the first alarm may have been a diversion. Callen believes that whoever set up the test must be watching from somewhere nearby. Nell looks at pedestrians who are nearby watching the scene. Nell recognizes one man as Griffin. The man enters a subway with Hanna and Callen following close behind. Griffin moves onto the tracks rather than be arrested. He trips and falls and Hanna and Callen move onto the tracks to lift him out before he is hit by an oncoming train.
Hetty faces off against Griffin in questioning. He remembers her as the woman who ruined his life. Hetty says that he swore he was innocent yet they are back in the same position. She offers that he help to save lives in order to help his children. Hetty asks what the target is and Griffin says he doesn't know. She tells him it's over but he was just running scenarios and collecting data. He needed the money but doesn't know their target. Griffin says the data is encrypted but it won't take the Russians long to crack it.
Eric informs the team that the house Griffin identified belongs to the Russian consulate and is therefore considered Russian soil. Callen says that isn't a problem as long as they are caught. He does warn that they could be in for a lot of trouble if anything goes wrong.
The team plans an elaborate ruse in order to make the Russians leave the house. They leave the house out the front door while Callen and Hanna sneak in the back. There is still a man in the house and he walks into a room where a man is doing something on a computer. One man tells him that he can continue working on the plane. Hanna heads up the stairs and creates a diversion to draw the man out. Hanna and Callen both attack a man and knock them out. Callen grabs a hard drive and makes his way out. Kensi tries to prevent the Russians from entering the house but one man flashes a gun and shoves his way in. Callen and Hanna jump out of an upstairs window onto a truck that Deeks has driven up the driveway. They make their getaway as the Russians shoot at them.
Granger enters the headquarters and tells the team they better not have been involved in the gunfight with the Russians. They retrieved the technology but Granger believes it will destroy relations with the Russians. Hetty points out that they can't say anything without admitting that they stole the files to begin with. Granger gets off the phone with the secretary and tells them that they dodged a bullet this time.