A man is riding a jet ski towards a local beach. The patrons of the beach notice that he is not slow down. As the Jet Ski hits the beach, the man is thrown off and lands face down. Several bystanders rush over to him and turn him over, he is not breathing. Preparing to give him CPR, they unhook his life jacket to find him bleeding from the chest with a bullet wound.
Sam and Callen are discussing Callen's living issues and Callen states he is thinking about a boat. Dominic asks about what happened to the agent that he replaced and the group nervously answers, that he had allergies & did not like the temperature. Sam asks Nate about his office and he states he is not going to question Hetty about the completion date, as he is clueless as to Hetty. Hetty calls just as he finishes the statement.
The team heads into the briefing room for their next case, the man on the Jet Ski was Daniel Su. He defected from North Korea and has been working as an electrical engineer for his own company. He was given funding from DARPA for a new project for the Navy. The team is impressed by the ability of the shooter to hit a moving target. They also realize that the shooter new the routine of Daniel, as he rented the Jet Ski at the same time every week.
Hetty finds Nate reading a comic book and questions him about his reading material. He notes that it is a graphic novel and she tells him that she is clueless about such things. She asks Nate how Dominic is doing and he states that Dominic is anxious to prove himself. She inquires if he knows that the three agents before him did not "pass muster" and Nate states he does not. Hetty tells him that it is best he not find out.
Sam and Callen head over to Daniel's home/office to see if they can find any leads. The home has been searched and they find a woman's dead body on the floor. They discover that the woman was Sally Morris, Daniel's business partner.
Back at their offices, Eric has found footage from the Marina and they can pinpoint the exact time Daniel was shot. Nate notes that the life vest acted as a pressure bandage and slowed the bleeding. They again are impressed by the shot and realize that the shooter must be a professional. Director Vance enters the room stating that they believe they know the shooter, Lee Wuan Kai. He explains that she is a dangerous assassin and he believes that she is killing off anyone who knows about what Daniel was working on. He notes that Daniel had a brother, Jimmy Su, who married an American Woman, Aimee. He tells the team that they refused to go into protection, but he ordered a team to sit on the house.
Callen and Sam head to the marina, continuing the earlier discussion of Callen's living plans. Sam suggests and RV, but Callen does not like the idea of a trailer, he is still interested in a boat. Sam asks him if he knows how to sail a boat and Callen states he does not.
Director Vance is not pleased that it will take so long to get an assessment of the crime scene from Daniel's house. He has Eric contact Abby Sciuto, from the Washington NCIS staff. He asks her to take a look at the pictures and get back to him as soon as possible. Eric sends the information to Abby. Vance heads into Hetty's office asking her how she is settling in. She tells him that it is fine; she just moves everything form one place to another. She stated that she would have made him Xiao Hong Pao tea had she known he was coming. He states that he would have brought her the Emilio Pucci Scarf, which Hetty notes that he was been promising her for many years. As he looks around the office, he notices a photo of Hetty and Olivier). She explains that they were on the set of Inchon. Vance realizes she is making a reference to the case and asks her, "Is there anything you don't know"? Hetty responds, "Oh, many things, I'm sure". They discuss this case.
Vance explains that he has had several run ins with this assassin beginning in 1984. As Vance leaves, Sam notes that Vance must have lost those run ins.
A meeting has been arranged with a representative of DARPA and Sam & Callen are sent to meet with Frank Davis. He states that the information Daniel was working on died with him and no one else knew about his research. Sam tells Callen that he believes that Callen has issues with bureaucrat, just a Vance calls them. They tell Vance what Frank said and that they don't believe him. Callen tells Vance that what Sam said and Vance points out that he is a bureaucrat. Callen quickly covers by stating that he does not have issues with him directly.
Sam and Callen head over to Daniel brother's home, in time to see Jimmy Su walking out of his home, screaming at his wife. As they head toward the house Sam sees a reflection, realizing it is from a scope he yells and they run to grab Jimmy. They seek cover behind a parked car, as the shooter escapes.
At the safe house, Callen, Sam, Kensi and Nate discuss the events with Jimmy and Aimee. He states that he knows nothing about his brother's work. They explain that he may need to relocate which includes changing their names. Jimmy states he is not interested in relocating.
Eric was able to track down the car that the assassin rented and finds out she is going by the name, Kim Andrews. He then is able to find her hotel reservation. Vance heads over to the hotel and calls Callen and Sam to meet him there. After Callen and Sam leave, Kensi notices that the couple are starting to fight. She begins reading their lips and finds out Jimmy knows a lot more about his brother's work.
At the hotel, Vance gets there first and heads upstairs. Callen calls him as they reach the hotel and Vance tells them to stay in the lobby. He lets himself into the room and finds it is empty. As he is looking around, he receives a call on the room phone; it is Kai. Vance dials Callen on his cell and puts the cell up to the room phone. Callen has Sam call Eric and they begin tracking Kai. Kai tells Vance that she did not kill Sally Morris. Kai is still in the hotel; Eric leads Callen & Sam to her location. Kai is gone, leaving her phone behind.
When Kensi shares that Jimmy knew a lot more about the business, the team suspects that maybe Jimmy killed Sally. They come up with a plan to trick Jimmy into confessing, only they need someone he has not met, Dominic. Hetty briefs Dominic and gives him the uniform of a LAPD officer, with a microphone and camera buttons on the pockets. She tells him she expects the uniform to be return in good condition, with no bloodstains. Dominic contacts Jimmy pretending to one of the LA police officers that responded to a complaint at the murder scene. He convinces Jimmy to meet him and states that Sally was barely alive when he got there. She whispered a secret to him and for the right price, he will share it with Jimmy. While they are talking, Kai is taking aim, as Sam and Callen watch is a parked car. Eric realizes Kai is there and alerts the team and Dominic grabs Jimmy and pulls him down as Kai starts shooting. They take cover as Sam and Callen locate her position at the top of a parking garage. When Sam reaches the location she was shooting form, she is gone. He sees the car racing out of the garage and chases after it. At several points, Sam is able to get several shots off and hits the car. As the car exits the garage, it slams into another vehicle. The team runs up to it, opens the driver's door and finds the seat empty, covered in blood.
Back at headquarters, Eric and Vance receive a call from Abby, she has finished analyzing the photos. She states that there was a handprint of the lamp, which was the murder weapon, but it was too smudged to get a fingerprint match. She then states that there was something odd about the handprint; there is a gap in the left hand second fingerprint. They realize that it is a set of rings and deduce that the killer must be Aimee Su. When they question her, she admits that she was there and that Sally was really mad about being deceived. Daniel was not the brother with the technology, it was Jimmy, Daniel wanted the recognition and Jimmy didn't. Sally threatened to contact the officials and stated she would have Jimmy deported.
Nate and Vance have arrived to assist in the search of the garage. They find no evidence of Kai, but based on the blood loss, if Kai does not get medical treatment for her wound, she will be dead. Vance leaves and Nate notes that this won't end Vance's obsession with this woman. Dominic realizes he lost one of the buttons off the uniform and it was the camera button, Hetty's camera button. Everyone starts looking for the missing button.