The ATF raids a drug lab, accompanied by a documentary/camera crew from the reality show, "On the Line". When they bust in the door, they find several dead Marines.
Sam arrives at the office to find Hetty waiting for him; she reminds him that he needs to complete his assessment of the "potential" new hires. Sam tells Hetty "Dom is missing, not dead". Hetty explains that the team needs help until Dom returns, but Sam disagrees stating, "This isn't an office job, we don't need a temp." Hetty tells him to complete his recommendation. The rest of the team is in the operations room, waiting to be briefed. As Sam enters, Eric begins showing the video footage from the ATF raid. Eric states that he has run facial recognition on the dead men and they were not Marines. The team questions why they would get involved and Eric explains that the uniforms and ID's were real. Hetty states that the director wants them to figure out where the uniforms came from to determine if there is a security problem.
Sam and Callen head over to the lab and look around. They find dead animals outside and have them tested for cause of death. Callen receives a call from Kensi reporting that Eric found a link to an address and the home is owned by Balmore. They head over to the home and find an elderly woman in the backyard. The woman is Esther Balmore and they show her pictures of the dead men. She states that they were her drivers and slips stating she was working on a top-secret project for the government. They remind her that they are the government and ask her about her work. She explains that she was working on isolating a strain of botulism and creating an antidote. She is escorted to the boathouse and Nate is sent in to determine her level of culpability.
The men in the house died from botulism poisoning, which makes Sam worry that they may have been exposed. Nate leaves the interview room and explains that Balmore is mostly likely in the early stages of Alzheimer's. It is believed that Balmore helped these men create a bio-weapon and that they may have enough botulism to kill millions of people. Eric found an identity on one of the dead Marines, Ian Albers and states he worked most recently for their "old friend" Dallas as a bouncer. Callen remembers that the last time they investigated Dallas, they were ordered to stop and he expresses his concerns to Hetty, while she is examining him for exposure to the botulism. Hetty ignores Callen explaining that deniability is a girl's best friend.
Eric finds out that Dallas has a standing appointment at a local spa and the team heads there. When the get to The Ahimsa Retreat Spa, Sam goes into his massage room, kicking out his masseur. Since Dallas is face down, Sam asks him questions, without giving away his identity. Dallas tells them that "The Dutchmen" is selling the botulism
Back in the Operations center, Eric explains that "The Dutchmen" is a well-known arms dealer, but his real name is not known. Eric notes that he has more aliases that Callen, including Sebastian Boon, Jurgen Vanderveen and Jacobus Troyger.
Hetty approaches Callen to discuss the issues with Sam and his feelings about a new team member. Hetty wants him to "nudge" Sam to make a decision regarding the new recruit and to help him deal with the loss of Dominic.
Eric informs the team that a man, Simon Amputuan has entered the country and has connections to several terrorist cells. The teams heads out to capture Simon and takes him to the boathouse. He denies any involvement with this group. They tell him that they have the "Dutchman" and they are giving him the first chance to talk. They ask him if he really believes that the "Dutchman" will protect him. After a few threats from the guys, Simon admits he has heard about the deal and that the weapon is due to be auctioned.
They decided that they need to take Simon's place at the auction and Sam is chosen to go undercover, since he has been vaccinated against botulism. He dresses in a suit, with a hidden camera and gets ready to head in. They know he will be scanned at the door, so they will turn the camera off remotely and then turn it back on once he is safely inside. He will not be allowed any weapons inside, so Hetty shows him his briefcase, which is bulletproof and has ceramic blade in the handle. Hetty also gives him a pen which is a hypodermic needle containing an experimental botulism antidote. Simon gave up his invitation, which is only visible under UV light to complete Sam's cover.
Sam heads to the pickup point, as Callen and Kensi monitor him from a distance. A man approaches Sam and then walks away, only to turn around and ask for directions. Sam explains that Simon was capture getting off his plane and he is there to make a deal. The man calls his boss and then escorts Sam to the car, putting a hood over his head. Outside a warehouse, Sam is introduced to the "Dutchman", who is using his alias of Jacobus Troyger. He agrees to allow Sam to take Simon's place and he is taken inside the warehouse. The camera is turned off and Sam passes through security without incident. Once inside, the camera is turned back on, but the signal is unclear. Eric states that there is another signal interfering with the camera.
Jacobus brings out the vial of botulism and he gives everyone in the room the vaccine. He explains he has demonstration planned. He directs their attention to the screen; he explains that they are looking at a live image of a local mall. He explains that he has a man in there who will release the botulism.
Outside Callen and Eric narrow the choices to two malls and Eric is instructed to send teams to both. Callen tells Sam that he needs to stall the auction while they secure the man in the mall. Callen and Kensi take off to help search one of the malls. Sam questions how the buyer will be able to get the vial out of the country once this test goes off, it will heighten security everywhere. Jacobus becomes suspicious of Sam and orders his men to search him. Sam distracts the men by investigating a fight between two other buyers, who dislike each other. Sam is able to capture Jacobus, as he tries to escape.
Hetty has Balmore looking at the security footage for the two malls, hoping she will recognize someone. She does and it happens to be the Mall that Callen & Kensi are searching. Hetty tells Callen & Kensi the location of the suspect and that he is carry a backpack, probably with the toxin inside. Nate has been watching the footage and states that the suspect is getting ready to release the toxin. Kensi catches up to the man in the food court and using a tray of food runs into the man. She grabs his backpack only to be tackled by the man and he runs off with his backpack. He runs towards the escalator, Kensi pulls out a gun and orders him to stop. He reaches in and pulls out the vial, as shoots him the vial falls over the edge of the second floor. Callen is on the lower level and sees the vial falling. He jumps up, reaches out and is able to catch the vial. As he hits the floor, the vials cracks and cuts his hand. Sam comes out of nowhere, grabbing Callen, pushing him into a nearby fountain. He injects Callen with the antidote pen Hetty gave him earlier, holding his hand and the vial underwater until the hazmat team arrives.
Back at the office, Callen states that the FBI is taking credit for the bust and Kensi is upset, it was their bust. Callen points out that they don't exist and Kensi tells him that he likes it this way. Hetty comes in and tells then that the mall is billing them for the fish that died in the fountain. She explains that the mall is stating that they were Koi fish, a very rare and expensive fish and the bill is $72,000. She stated that she has requested the corpses of the fish so she can verify that these are really the Koi fish before paying the bill. Nate tells Hetty that he is recommending that Balmore not be charged and that she needs to go into a nursing home. Hetty states that she is not going to be charged and heads to her office. Callen senses something is off with Hetty and follows her to her office. Hetty explains that it is not the lineless that she fears but that she might tell all of her secrets. She then tells Callen that when the time comes, she wants him to smother her to with a pillow. Sam has left the office and heads over to Balmore home to help her with her gardening.