After a famous crossword puzzle master is found in an urban fracking site, the Jeffersonian team investigates puzzle champ’s fellow players in order to track down the killer. After discovering that the victim was suffering from a mental illness when he died, the team realizes the case is much more complicated than it seemed. Meanwhile, a very pregnant Daisy seeks comfort from her doula, Valentina , and the newest member of the Jeffersonian family arrives.
Gibbs and McGee travel to Russia to safely escort home an NCIS computer engineer connected to classified intel, but their mission is compromised and they are forced to go off the grid while hunted by a Russian mercenary group.
NCIS looks into the disappearance of a Navy lieutenant commander who is working on foreign cyber threats with the NSA; the team celebrates the holidays.