After the U.S. Treasury Department is hacked, Nell and Eric go undercover inside a couple's retreat to track a tech-savvy husband and wife linked to the crime. Also, Digital Forensics Specialist Dave Flynn arrives from the NCIS cyber office in San Diego to run ops while Eric and Nell are on assignment.

The NCIS team investigates a defense contractor, Rebecca Larmont, designing a nuclear attack weapon after her estranged husband, Victor Larmont, says he has proof she is selling Navy secrets to a foreign government. Also, Kensi goes undercover as a professional dancer at the Cuban club where the husband works, while Deeks is undercover as the bathroom attendant.