The body of a Marine leads Gibbs and McGee to the NCIS OSP division in Los Angeles, where a murder investigation quickly climbs to a matter of national security in which the two offices must work together to resolve. Meanwhile, Tony begins to snoop into Ziva's personal life.

With the appearance of Mossad agent Michael Rivkin, Tony is forced to question Ziva’s loyalty to NCIS. Meanwhile, in Los Angeles, Special Agent Callen goes undercover to try to catch a terrorist cell while OSP psychologist Nate Getz discovers the startling truth about Gibbs and Special Agent Lara Macy’s relationship.