Nell returns at Hetty's request after her mother's death. Even though Nell hasn't returned to work at NCIS, Hetty wants her to run point on an investigation of a missing Russian bomber. Nell calls Kensi at the Squid and Dagger, to have her and Deeks report. Fatima catches up Sam and Callen. No one knows where the bomber is. Eric is away on personal business. Roundtree has joined NCIS and Nell sends him to surveil the unofficial Russian consulate. Kensi talks with Nell about her mother's death. Sam and Callen speculate the bomber may have crash-landed. Fatima finds reports on UFO web sites of an unidentified plane near a national forest. Nell gives them a chopper to check it out. Arkady shows up at the bar. Kensi and Deeks ask him to make some calls about the bomber. Arkady gives them the name of a Russian spy to interview, Sasha Gagrin. Sam spots the plane just as they're about to turn back. Two crew members are still with the plane. Callen tries to talk to them but Sam and Callen get fired upon by the tail gunner but they hide under the plane. Sam follows footprints while Callen tries to establish communication. Deeks approaches Gagrin disguised as a homeless man and offers her money but she brushes him off. Then she gives him a bag with names of the crew members written in it in exchange for the money. When Callen calls to them by name, they arm the plane's self-destruct mechanism. Callen speculates that one of the crew may have tried to defect and is shooting at the others. The rest of the team arrives. They capture the four in the field. The unarmed training plane blows up after Callen talks the other two crew members into surrendering.