The NCIS team investigates the murder of Navy Captain Mason Green, who was poisoned and left in an alley after watching The Nutcracker with his daughter and her husband. They discover, much to their curiosity, that Green had Ducky's old address in his pocket.
They soon learn that Green was under investigation for selling Navy secrets, and there was a bank account in Crimea under Green's name. Green's last phone call, however, was to a phone registered to a Balthazar Kilmeany.
Ducky recognizes the name as his mother's former fiance, who Ducky had discovered was actually a conman and sent packing, despite his claims to genuinely love Victoria.
The team learns that Green did not steal the Navy files and that he was set up, by someone using the Kilmeany alias. Prior to her death, Ducky's mother Victoria had seen a man at the theater who she thought was Balthazar.
It's not long before the team puts it all together and realizes that the captain's son in law is the current Kilmeany (and nephew to the former Kilmeany).
Ducky, meanwhile, is surprised and heart-warmed to learn that her mother during her later years had taken up with Mr. Rin, the gardener, and so did not die heartbroken and alone.
Emily Fornell successfully enacts a devious plan to force her father off of Gibbs's couch and back to his own home just in time for the holidays... unfortunately for Tobias Fornell, this plan involved termites, so Gibbs gets sweet revenge by bedding down on Fornell's couch.