NCIS: LA gets called in to find their liason, LAPD Detective Marty Deeks, who has gone missing after a target of his undercover investigation is murdered.

The team is debriefed by the case officer in charge of Deeks' undercover operation, Det. Traynor. She tells them that Deeks' infiltrated a local street gang whose leader, Emilio had ties to Lazik, a Serbian national who runs an international human trafficking ring.

Deeks suspected that the two were working to create a human trafficking ring across the U.S-Mexican border until Emilio was killed in car bomb.

When Det. Traynor is also killed in a car bomb the team knows they must act fast to find out if Deeks is still alive.

The new lead LAPD officer in the investigation, Scarli, is less than cooperative with Callen and the team.

Deeks finally makes contact with Hetty and tells her that he wants to follow through with meeting Lazik. He wants to try and catch him in the act of smuggling young girls from Mexico in order to finally bring him to justice.

Hetty tells Callen to keep a close watch on Deeks, so when Deeks' meeting with Lazik turns dangerous, Callen and the team move in and help bring Lazik down in a fire fight.

It turns out Lazik killed Emilio because he found out Emilio was working with Det. Traynor to bring him down. Lazik's source was a dirty LAPD cop on his payroll ... Scarli.

Deeks arranges a meeting with Scarli, who has no idea NCIS knows Deeks is alive. Scarli admits everything and is about to kill Deeks when Callen and Sam bust him.

Meanwhile, Hetty is sending Nate on a mysterious mission that is so secret, even Nate is not given any details, and Callen is still struggling with putting the pieces together of his past and identifying the man who was watching him at the cemetery.

Hetty stuns Callen when she buys a new house for him, he is resistant at first until he sees the address - it's Alina's house.