Members of the team go undercover at a university in order to track a hacker who is putting the world economy at risk. Walter conducts an experiment to prove that Ray's partner's death was not his fault.
The team must work with Toby's nemesis and his wife -- Toby's ex-fiancée -- when they are locked inside an artificially intelligent doomsday bunker that aims to kill them; Walter is distracted by a dream in which he married Florence instead of Paige.
In an effort to find the terrorist Parsa, Gibbs and the NCIS team track down one of his cohorts using evidence from the drone attack. Meanwhile, an emotionally shaken McGee struggles with the ramifications of the incident.
A murder in an underwater lab sends Adam, Junior and Tani to the ocean floor, where the killer is still at large and perhaps even hiding onboard.
A bus full of tourists is hijacked by gunmen demanding $18 million. With the help of a video feed from inside the bus, Don and the team race against time to waylay the hijackers.