The episode begins with a woman arriving in a parking garage. She sees three men walking towards her. She tries to run. She finds another man standing next to his car and she asks him for help, but one of the three men, shoots him. One of them manages to grab the woman. At the office, Sam tells Callen to dress up as professor Lupin, a werewolf, for his daughter’s birthday party. Callen reluctantly agrees. Kensi is cleaning her gun with Deeks’ t-shirt when Deeks arrives and tells her that he had that t-shirt since high school. He says that it was his rock band’s uniform.
Kensi is surprised and wants Deeks to sing, else she would tell Callen and Sam about Deeks’ band and they will use all the available technology to dig out the footage of him singing. Deeks begins to sing (he is terrible) when Eric arrives and tells them that Hetty wants them in ops. Nell tells the team that a woman was attacked by three men and two of her attackers, along with a by stander, have been killed and the woman is missing. Callen wants to know why they need to solve this case. Hetty tells him that ‘she’ wants them to solve this case. They don’t find any leads on the woman and the attackers. Hetty tells them to find out about the attackers’ identity.
Kensi and Deeks examine the dead bodies, but they don’t find anything. There are no ids and fingerprints. The facial recognition also came up with no results. Sam and Callen examine the crime scene and Sam finds a lot of blood on the stairs. He sends Eric some pictures. Hetty looks worried. The team comes back to their desks and Eric tells them that Nell found some additional footage from outside the garage. They see that he woman tackles her attackers and ends up gunning down two of them, and the third attacker was also shot, but he survived. Everyone is amazed. Sam thinks that the woman is a professional.
Kensi wants to know who the woman is. Callen wonders why Hetty is interested in this woman. Hetty arrives at the boat house and knows that the ‘mystery woman’ is hiding there. She is glad to see that the woman is fine and the bullet just grazed her. At the office, Sam and Callen figure out that Hetty is holding out on them. They also know that Hetty is protecting the mystery woman. Callen and Sam arrive at the boat house because they figured out that they might find Hetty there. Callen wants answers. Hetty tells them that the woman’s name is Grace Stevens and that she is one of theirs.
Later, Grace tells Callen and Sam that a guy named Nolan Vandenberg, who came up on their radar, has been supplying equipment that could be used to facilitate the enemy’s nuclear program. She says that she went undercover and lived with Vandenberg for three years and worked with him for 11 months, but she wasn’t able to find who he is supplying to. She says that when Vandenberg found out about her, he sent his men to kill her. She feels that after last night, Vandenberg might have fled the country.
At the OPS, Nell tells the team that Vandenberg’s company has purchased a property in North Mexico. Nell also finds out that Vandenberg has not left the country and he has booked a three bedroom suite at a hotel in Baltimore. Callen tells Eric to find out more about Grace and her reason to join NCIS. Eric fears that he might run into trouble. Callen tells him that he won’t, if he doesn’t get caught. Next, Deeks and Kensi pose as a couple and book a suite in the same hotel. Callen and Sam are in the lobby. Nell poses as the housekeeping staff. Kensi fixes a button camera on Nell’s uniform. Callen and Sam spot Vandenberg in the lobby.
Nell goes into Vandenberg’s room and goes through his briefcase. She finds audio and video bug detection devices, and she disables them. At that moment, she hears the sound of the flush. She quickly places the briefcase back in its original position. A man with a gunshot wound walks out of the bathroom. Grace, who is watching the team from ops, identifies him as Visser, one of her attackers, who she shot. She tells the team to get Nell out of there. Kensi poses as a member of the Hotel Management team, and manages to get Nell out of the room. In the lobby, Sam and Callen see that two men arrive to meet Vandenberg. Grace tells them that she has never seen them before. Eric runs a facial recognition, and finds out that they are attachés from Niger and Namibia, the third and the fourth largest suppliers of Uranium.
Callen notices that they handover a case to Vandenberg, and he decides that they should get hold of it and Vandenberg. Callen tells his team to be in position. Visser leaves his room to go to the lobby. Kensi tries to stall Visser, but she fails. Deeks and Nell are in position. Everyone waits for Callen’s orders, but Callen aborts the operation. At the ops, Sam tells the team that they should bring in Vandenberg. Grace tells them that with Vandenberg out of the picture, the attachés will look for other suppliers. Deeks suggests that they could set up a bogus company and act as the ones who could supply them with the equipments. Everyone likes the idea. Callen goes to ops and asks Eric if he managed to locate Vandenberg.
Eric tells him that he has no clue as to how he exited the hotel. Eric hands a flash drive to Callen. It has Grace’s history in it. Eric tells him that Grace’s past is very much like Sullivan’s, Hunter’s and his (Callen). Callen goes through the contents of the drive. Sam arrives and notices that Callen looks slightly disturbed. He asks Callen what’s going on but Callen doesn’t say anything. Callen confronts Hetty. He knows that Grace was an orphan just like Sullivan, Hunter and him, who Hetty plucked out of an orphanage, trained them and recruited them into NCIS. He wants to know how many of them has she done that with. Hetty loses her cool and yells “A lot”. Callen leaves.
Later, Callen and Grace have a short conversation. During the conversation, Callen has a new idea. He tells Grace that since Vandenberg still wants her dead, they could use her as a bait to lure him out. Next, the news channels broadcast about a woman who was attacked and left in an alley. It is Grace. At the hospital, it has been two hours, and the team is about to lose hope when Vandenberg arrives to meet Grace. The team manages to arrest him, Visser and another bodyguard. Case closed. Next, Hetty pours a fifty year old whisky for Callen and apologizes for losing her temper. Callen admits that he should not have instigated her. They have a long chat. The episode ends.