Sound Off is the 13th episode of NCIS Season 17 and also the 391st episode of the entire NCIS series.
After a body is found at an unmanned aerial vehicle testing site, the NCIS team must determine if the death was murder or an accident while Palmer carefully interviews medical assistant candidates.
- Jimmy begins looking for an assistant.
|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.|
|Eleanor Bishop||Emily Wickersham||Special Agent for the NCIS Major Case Response Team.|
|Nicholas Torres||Wilmer Valderrama||Special Agent for the NCIS Major Case Response Team.|
|Jacqueline Sloane||Maria Bello||NCIS Forensic Psychologist|
|James Palmer||Brian Dietzen||Chief Medical Examiner for the Major Case Response Team.|
|Kasie Hines||Diona Reasonover||NCIS Forensic Specialist.|
|Leon Vance||Rocky Carroll||Director of NCIS|
|Donald Mallard||David McCallum||NCIS Historian. Despite being credited, McCallum doesn't appear in this episode.|
|Diana Murphy||Katie Leclerc||Marine Staff Sergeant who is also deaf and the ex-girlfriend of murdered retired Marine Gunnery Sergeant Danny Backer.|
|Edison Geary||William R. Moses|
|George Ingram||David Burke||The killer.|
|Christopher Crane||Peter Graham|
|Zahir Najjar||Amir Korangy||Professor at MIT.|
|Ronald Kepczak||Adam William Zastrow||Marine Gunnery Sergeant Danny Backer's step-brother.|