Third Wheel is the 4th episode of NCIS Season 16 and also the 358th episode of the entire NCIS series.
Gibbs finds his quiet vacation at his remote cabin interrupted by a surprise visit from Tobias Fornell and Navy Captain Phillip Brooks, as well as a call from NCIS asking for his help locating a robber hiding in the woods near him.
- Gibbs takes time off from NCIS and has McGee temporarily take over in order to blow off steam from his earlier role as acting director.
- It is revealed that Jack Sloane had a falling out with a old acquaintance from the FBI due to losing her car in a bet.
- The production code for this episodes indicates it was filmed before "Boom", but aired afterwards.
|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. Despite being credited, Carroll doesn't appear in this episode.|
|Donald Mallard||David McCallum||Chief Medical Examiner for the NCIS Major Case Response Team.|
|Tobias Fornell||Joe Spano||Former FBI Agent who is now a Private Investigator.|
|Phillip Brooks||Don Lake||Navy Captain.|
|Susan Ottsley||Jill Czarnowski||NCIS Tech.|
|Isabel Monet||Kate Orsini||FBI Special Agent.|
|Anna Jenlowe||Emily Rose||FBI Special Agent|
|Muncie Tyson||Rich Ceraulo Ko||North Carolina State Trooper.|
|Kaitlyn Holcomb||Amielynn Abellera||Navy Lieutenant|
|Lovinder Prasad||Daryl C. Brown||Navy Commander|
|William Forman||Bo Kane||North Carolina State Trooper.|
|Horace Barnes||Ian Gregory||FAA Security Specialist|