When Viktor Varlamov is murdered by Dmitri Greshnev, one of arms dealer Isaak Sidorov's henchmen, the NCIS:LA team springs into action. The last time they saw Sidorov, he had stolen nuclear warheads and was looking to sell them on the black market, so the team thinks that this resurfacing means he may have found a buyer. Sam immediately worries for his wife's safety, since she'd gone undercover as an assassin for Sidorov, and he thinks Sidorov may have figured out that she's actually a former CIA agent. He goes to see Michelle, who insists they resume their undercover identities to foil Sidorov's plans - whatever they may be. Soon, Greshnev tracks them down and tells Michelle that she has 24 hours to kill Anatoli Kirkin, one of Sidorov's rivals. Sam tries to tail Greshnev, but he's pulled over by the LAPD, who find the weapon used to kill Varlamov in his car and arrest him. Worried for his safety and the integrity of their cover, Hetty tells him that she's not going to bail him out of jail, and to trust Callen and his teammates to keep his wife safe. Furious, Sam manages to break out of LAPD holding, just as his teammates stage Kirkin's death with Michelle's help. Michelle then meets up with Sidorov and Greshnev, with the team watching closely and ready to arrest them, but Greshnev spots the trap and warns Sidorov. Sam arrives just in time and shoots Greshnev to save his wife, but Sidorov escapes.