When Lala's favorite CI is shot, the team joins forces with Oceanside PD to determine who was behind the attack. Also, Franks visits his brother Mason at the compound, and Gibbs' relationship with Diane is tested when she gets a job in Los Angeles.

When a marine captain shows up at Camp Pendleton exhibiting symptoms of a fatal virus, NIS goes on lockdown and Gibbs is forced to take charge. As panic spreads, the team races to determine whether it really is a deadly outbreak or something else entirely.