One Russian kills another in the Los Angeles area; Callen and company investigate. G and Sam consult Arkady, a long-time Russian source; G suggests that, if Sidorov and Greshnev are back in the USA, then they have a buyer for the three stolen nuclear weapons, and Sam suggests that they seek his wife. Granger directs Hetty for the team to collaborate with Snyder, from the CIA, so Hetty directs Kensi and Deeks to keep Snyder busy and not to let him out of their sight. Sabatino, of the CIA, shows up at Sam's house; For the CIA Sam goes back undercover as David Forman, and Michelle goes under as Quinn; Greshnev demands that Quinn kill Kirkin; David tails Greshnev, but four LAPD cops stop David and arrest him, then Hetty leaves him in jail; Kensi makes a plan, and Deeks takes the point and makes a deal; Quinn "executes" Kirkin, David escapes, and Sam rescues Michelle; Greshnev dies, and Sidorov disappears. Hetty comments that this matter is far from over.