When nuclear detection technology is stolen, the NCIS team springs into action to investigate and they determine an attack on Los Angeles is imminent. Finding one of the thieves dead, a surveillance camera leads them to Central Park where they take down another suspect. Eric and Hetty work on interpreting a map at the house of one of the suspects while Nell investigates a man Hetty let go years ago since Hetty thinks he might be connected. When they finally catch him, he admits that the Russians have the technology and are holding it at the Russian Consulate. Knowing the consequences of breaking into the Consulate to retrieve the technology, the team plans an off the books operation to steal it back.