Gibbs obsesses over an old adversary who resurfaces in DC with a deadly plan (23/23).
Gibbs and McGee work with the NCIS Office of Special Projects (OSP) to track down a terrorist cell in LA. The agents question Ziva's loyalties.
When a sailor's body is discovered in an abandoned part of town, a drugs overdose seems the likely cause of death. But all is not as it seems.
The murder of a marine brings the team into contact with the Office of Special Projects in LA. Tony becomes concerned about Ziva's behaviour.