The NCIS team investigates a deadly car explosion in D.C. that connects to NCIS Special Agent Nicholas "Nick" Torres, who disappeared six months ago while on a deep undercover assignment in Argentina. Also, Gibbs asks NCIS Special Agent Alexandra "Alex" Quinn to shadow his team after rejecting eight agents she instructed and referred for the open position.

When the NCIS team investigates a marine sergeant's tragic fall from a building, her doctor, Grace Confalone, confides in Gibbs and suggests he treat it as a murder investigation. Also, Torres searches for a place to live.