In New Orleans, Louisiana, two local special agents of the NCIS, Pride and LaSalle, start to investigate the death of Dan McLane, who was not only a member of the US House of Representatives but also both a retired Naval Reserve commander and a retired agent of the NIS (before the NCIS); Dan had worked with Franks and had served as a mentor to both Pride and Gibbs; King Pride, a former partner of Gibbs, goes to Washington, DC, and spends time with Gibbs. Inter-agency intrigue begins; the FBI seizes control; a joint FBI-NCIS effort proceeds; Fornell joins the hunting party; the Gibbs team start producing results; King and Gibbs use an old-school technique; LaSalle in Nola says that he suddenly feels new respect for the Great Lakes office. An FBI agent in Nola dies in the same way as Dan; King goes back there, and Gibbs and Ellie go with him; Abby provides answers; the bunch in Nola follow the breadcrumbs left for them. [To be continued.]

While investigating the death of a US congressman, the Gibbs team and the gang in Nola continue to seek both a killer and a connection to an old case. Another man dies. Ducky suggests a theory, and the bunch put all the pieces together.

Gibbs and his team work with Pride and the New Orleans team to find Abby's brother and figure out why the passengers and crew of a private plane he catered were poisoned.

When Abby's homeland security think tank is compromised, the team realizes that a theoretical terror playbook has been stolen.