Viktor Varlamov is killed in a park, which leads NCIS to believe that Dmitri Greshnev and boss Isaak Sidorov have returned to the United States. If they are back, they will want to know why Sam's wife, as an undercover assassin Quinn, hasn't killed Anatoli Kirkin yet. Sam and Michelle are forced to resume their cover identities. Plus, NCIS continues their search for the three nukes that Sidorov stole from the homes of KGB agents in the US.
CIA agents Michael Snyder and Vostanik Sobatino arrive to assist with the case.
Greshnev and Sidorov plant the ice pick that killed Varlamov in David Forman's (Sam) car and he is pulled over and arrested. Instead of bailing him out, Hetty decides it would be safer for him to remain behind bars. Sam attacks a prison guard and escapes in order to protect his wife.
Kensi suggests that NCIS fake kills Kirkin and then tracks Sidorov to the nukes after he meets with Michelle. Deeks meets with Kirkin to get his agreement to help with the plan. Michelle/Quinn enters a bar and "shoots" Kirkin dead. She then goes to meet with Sidorov for her payment. They want her to go with them since her face is all over the web shooting Kirkin. She doesn't want to go with them. The Russians make the CIA agents on the basketball courts and starts shooting and kills Agent Snyder.
Sidorov takes off in a lifeguard truck, while Greshnev takes Michelle. He thinks she was responsible for the agents being at the meet and pulls a gun on her. Sam shows up just before Callen and kills Greshnev. Sidorov got away, so as Hetty said, "This is far from over."