NCIS partners with the FBI after a Marine is murdered by a rare nerve gas. Also, Deeks shares his dream to quit law enforcement and open a bar.

After a rise in deaths caused by black market opioid use, the NCIS team links the street drug to funding for terrorist activities

As Callen continues hunting Katya, Kilbride enlists NCIS to help find a truckload of stolen guns. The assignment becomes more challenging when their suspect, the son of a mob boss they believe was planning to sell them, is found dead.