Karan Oberoi

Beckett and the 12th Precinct look into the murder of an English as a Second Language student. When the victim's class won't talk to the police, Castle goes undercover as a French Canadian immigrant and learns the victim was more than he seemed.

The Department of Defense, including Gibbs' ex-girlfriend, helps the team search for a stolen drone linked to an elusive terrorist.

The team must find assailants who illegally crossed the border and attacked California Highway Patrol officers; Homeland Security sends Nell's older and bossy sister to assist with the case.

A port authority officer's murder reveals a possible location for Parsa; Bishop reveals a past connection to the terrorist.