While NCIS investigates the murder of a Navy intelligence officer killed during a conference for foreign diplomats, the key witness cozies up to Sebastian. Also, Pride has some trouble adjusting to his new position at the agency.

The team places Mateo Diaz, a high school gang member turned informant, in protective custody while they investigate the murder of his junior reserve officers' training corps instructor; Pride needs his brother's help to gain Mateo's trust.