Gibbs and Bishop are on a nuclear submarine, conducting an investigation into the death of a Navy SEAL. However, things take a turn when the submarine dives for a mission with Vance later learning from the Pentagon that the submarine has gone radio silent while McGee and Torres race against the clock to find and stop the person responsible for the actions that the sub has taken and before the submarine in question is shot down at sea to prevent it from striking out against Russian submarines in the area.
- Ducky officially retires as the Chief Medical Examiner and becomes the official Historian and archivist of NCIS.
- Bishop is revealed to be uncomfortable operating within vessels, in particular submarines.
- This episode aired on the birthday of voice actor, Kazuhiko Inoue who is the official dubbing actor for Leroy Jethro Gibbs (Mark Harmon) in Japan.
|Leroy Jethro Gibbs||Mark Harmon||Special Agent in charge of the NCIS Major Case Response Team.|
|Timothy McGee||Sean Murray||Senior Special Agent and second-in command of the NCIS Major Case Response Team.|
|Nicholas Torres||Wilmer Valderrama||Special Agent for the NCIS Major Case Response Team.|
|Eleanor Bishop||Emily Wickersham||Special Agent for the NCIS Major Case Response Team|
|Jacqueline Sloane||Maria Bello||NCIS Forensic Psychologist|
|James Palmer||Brian Dietzen||Medical Examiner for the Major Case Response Team|
|Kasie Hines||Diona Reasonover||NCIS Forensic Specialist; Abby's replacement|
|Leon Vance||Rocky Carroll||Director of NCIS|
|Donald Mallard||David McCallum||Chief Medical Examiner for the NCIS Major Case Response Team.|
|Reginald Barkley||Matthew Bellows||Navy Captain.|
|Constance Shaw||Arlene Santana||Navy Chief of the Boat.|
|Justin Hardy||Tommy Walker||Navy Petty Officer First Class.|
|Gregory Pullman||James Ferris||Navy Lieutenant Commander.|
|Emily Ross||Michele Boyd||Navy Chief Petty Officer.|
|Zachary Harper||Ransford Doherty||Navy SEAL Petty Officer Second Class.|
|Jennifer Leo||Megan Gallagher||Under Secretary of the Navy.|
|Brian Kalr||Tracy Howe||Navy Culinary Specialist.|
|Alfonso Romero||Ethan Flower||Fire Chief.|
|Unnamed Chief of Watch||Josh Trant|
|Walter Miller||Mark Fite|