True Believer is the 8th episode of NCIS Season 18 and also the 406th episode of the entire NCIS series.
This episode also features the final appearance of Maria Bello (Jack Sloane).
When Sloane's name is discovered in Afghanistan at the site of an abandoned bus with a dead driver, Gibbs accompanies her on a trip to find a group of girls who were kidnapped from the bus while McGee, Bishop and Torres track down a hacker who emailed compromising information to the Taliban.
- Sloane resigns from NCIS and chooses to remain in Afghanistan.
|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.|
|Ben Mitchell||Michael Goldsmith|
|Eric Freeman||Javon Johnson||NCIS Special Agent, Middle East Field Office, Bahrain.|
|Samantha Watkins||Sarah G. White||AKA "Mom".|
|Yazmin's Mom||Hedyeh Falsafi|
|Marine (True Believer)||Manny Cartier|
|Abu Muhamad||Marco Khan||AKA "Kidnapper".|
|Albert Gorsch||Daniel Lupa-Chazan|
|Kidnapper||Roman Mitichyan||Uncredited role.|