Dom shows up as a prisoner on a jihadist website; the OSP team swing into action; Sam sees his friend Moe; a runner provides a lead to a wealthy source of funds for terrorism; Dom escapes with help, and Sam finds him but not soon enough.

Both Alex and Jada, from Sudan in a previous episode, have reappeared in Los Angeles; while two NCIS agents (on a protective detail) escort Jada to an office in preparation for her giving a deposition, a masked man in an SUV attacks the trio in their car and escapes without injuring anyone. Kensi and Deeks get a name from Jada, then check a warehouse and catch a bad guy; Alex and his family disappear; Sam offers to play water games; Nell finds Alex, then the foursome chat with him; his behavior perplexes everyone; Kensi and Deeks visit an international business firm, from which they acquire important data; Alex finds the gang, surprises them, and chats them up, then they all pitch in and change their plans. Alex calls the main middleman and proposes a deal, which blows up; Alex gets his family back, and the gang keep Jada but lose the middleman, although another agency catches him later.

After the decryption of a list of names, NCIS agents continue the search for both Sidorov, a Russian illegal-arms dealer, and leftover Russian sleeper agents with access to surreptitious nuclear bombs; NCIS teams execute concurrent arrests in seven cities around the USA; however, all seven teams find their targets already dead. G and Sam confer with Arkady; afterward G and Sam meet a tail, which consists of three CIA agents, one of whom, Snyder, Sam knows and dislikes; Kensi, Deeks, and others uncover an empty but radioactive secret room; Eric and Nell find Sidorov; Granger gives an order, but Sam pursues another idea, and Granger catches the team, yet he goes their way; the team watch Sidorov; Sam goes undercover, then he and his wife meet with Sidorov; Snyder allows Sidorov to leave the country (without bombs), but he expects him to return; Sam and Snyder walk into the surf at Santa Monica Bay, where the two of them discuss a disagreement.

Hetty goes rogue and an agent is kidnapped by the mole.