FBI Special Agent Mia Calvillo is murdered while searching for missing undercover agent Devin Roundtree. Nell, who suspects Anna is still in L.A., offers to help Callen find her. Sam is sparring with NCIS Special Agent Sutherland when Eric cuts in, asking to wear the mitts while Sam punches them. Sam's son Aiden is in town so Callen gives Sam time off. Deeks also called in by LAPD to help with a case. Hetty has reassigned Fatima to L.A. permanently. DOJ Special Agent Lance Hamilton will be joining the search for Roundtree. Callen and Fatima decide Calvillo walked into a trap. Fatima tells Callen she wants to work now instead of taking time off. A stoner named WIlly caught the shooter on his boat's surveillance. Nell tracks down the shooter's getaway vehicle and Fatima and Callen go to investigate. Aiden got into flight school. Kensi lights up a truck to empty Usman's house while Cejudo searches it. Cejudo is surprised by Usman, their only lead, and kills him. Callen and Fatima locate the shooter holed up in a vacant house but he escapes on a tow truck. It's Roundtree.  Callen tags him so the Overwatch program could track him. Usman's bodyguard thinks Kensi is a dirty cop. Roundtree is holed up at a closed supermarket. Cejudo might be a dirty cop and he's with Kensi and Lance. Eric discovers that both Cejudo and Calvillo have huge offshore accounts. Sam joins the team at the supermarket. Roundtree surrenders to NCIS. Cejudo has brought in reinforcements, but they get picked off one by one, with Roundtree wounding Cejudo. Roundtree turns over incriminating evidence on the dirty cops to NCIS. Eric gets offered a partnership at a startup tech firm in San Francisco. Lance takes the team out to eat at the beach.