The team searches for a former IRA bomb-maker who was smuggled into the city, and are joined by Special Agent Hannah Khoury, Pride’s replacement during his medical leave. Also, Pride considers a new position with the agency.

Pride and the NCIS team hope to take down a secret and lethal group of former intelligence agents and avenge the death of someone close to them.

Pride and Lasalle travel to war-torn South Ossetia in Russia to locate FBI Special Agent Raymond Isler, who was kidnapped during a failed mission to apprehend the leader of Apollyon, the underground spy network responsible for murdering Pride's father.

After tracking Apollyon, a deadly underground spy network, to war-torn South Ossetia, Pride is separated from the team and faces grave danger. Also, in order to save Pride, the NCIS team must locate a mole who continues to feed information to Apollyon.