A killer murders a Navy officer, Lt. Commander Timothy Weir, while putting on a show for high-paying voyeurs. Hetty and Mosley are arguing in Mosley's office. Everyone is worried about changes. Mosley sets up new teams for the Weir case: Sam and Kensi and Deeks and Hidoko. Callen becomes Mosley's partner. They're working with the ATF trying to catch a weapons dealer: Spencer Williams. Kensi argues with Sam over who should drive. Hidoko deflects Deeks' attempts to learn more about her. They talk to Amanada Huang, a woman at the Chinese consulate who was dating Weir. The ATF undercover agent gets killed at the weapons buy. Sam and Kensi arrest Bobby Griffin, convicted of a mutilation murder 20 years ago. Mosley gets into it with the lead ATF agent, Char'isa Swan. Williams goes to Cole BIngham, who is Callen's informant, for a replacement. Callen goes in undercover. Mosley admits she was in a relationship about Williams before the theft. Hidoko says she would always be loyal to Mosley, her mentor. They trail Huang to an abandoned movie theater, where Deeks find a body hung up on a cross, with body parts from five different people. Huang is actually an NSA agent, and Weir was her partner. The FBI has been investigating two similar cases. So Weir's disappearance has nothing to do with national security. Swan and Mosley argue over having Callen arrest Williams before Williams flies away on a private plane. ATF moves in and seizes all the weapons. The FBI loses Williams at LAX. Callen senses Mosley isn't telling him everything. Mosley admits that Williams took their son, Derek, when he fled the country. She hasn't seen him in five years. Callen promises to help her. The body parts belonged to the actual people from the mechanic shop. The people they interviewed were the killers, including Griffin.