Despite several team members having grave reservations, NCIS travels to Mexico for a risky mission to locate and rescue Mosley's son.

After Sam is shot during a firefight with the cartel, a suspect is interrogated and reveals new information on the whereabouts of Spencer Williams, the man who kidnapped Mosley's son five years ago.

NCIS investigates the murder of a federal prison inmate who was the adopted daughter of a notorious counterfeiter. Also, Callen is summoned by the Alcohol, Tobacco and Firearms (ATF) Internal Affairs board to discuss Anna Kolcheck’s actions during a joint NCIS and ATF case.

NCIS partners with the FBI after a Marine is murdered by a rare nerve gas. Also, Deeks shares his dream to quit law enforcement and open a bar.

Callen, Sam and Nell must find pieces of a failed rocket launch, including a top-secret government device; Hetty tries to help Keane acclimate to life in the states.

After a cryptocurrency farm is robbed of over $10 million in Bitcoin codes, Sam and Hidoko go undercover, with Sam resuming a likely compromised former alias.

Callen and Sam join forces with Anna Kolcheck and the Bureau of Alcohol, Tobacco and Firearms (ATF), when Arkady Kolcheck warns NCIS that a notorious international weapons dealer has returned to the states. Also, the case requires Eric to go undercover as a bank IT technician.

While investigating a missing person’s case, the team uncovers a killer who puts on shows for high-paying voyeurs. Also, Mosley assigns Callen as her partner on a joint ATF mission to apprehend someone from her past.

Callen pursues every alternative when the Diplomatic Security Service apprehends his father, Nikita Aleksandr Reznikov, as part of an exchange for two American photographers being held hostage in Iran.

Callen and Sam pull Granger’s daughter, former spy Jennifer Kim, from witness protection to help the team locate an underground spy who has obtained an arsenal of bomb materials.