The Fifth Man is the third episode of NCIS: Los Angeles Season 4 as well as the 75th episode of the entire NCIS: Los Angeles series.
When a diner is attacked, resulting in the deaths of four people, all of whom were players of a new terrorist attack warning system called "Operation Wide Awake", OSP investigate and soon find themselves racing to save the fifth and final tester, a young autistic girl from suffering the same fate while Nell plays the game but soon discovers a potential flaw in it, one that could serve as a motive
- It's revealed that Kensi spent nearly a year living on the streets after her father died.
- It's revealed that Nell has an IQ higher than any other person who works for NCIS.
|G. Callen||Chris O'Donnell||NCIS Special Agent and the leader of the Office of Special Projects field team.|
|Sam Hanna||LL Cool J||A former Navy SEAL-turned-NCIS Special Agent with the Office of Special Projects.|
|Henrietta Lange||Linda Hunt||Operations Manager with the Office of Special Projects.|
|Marty Deeks||Eric Christian Olsen||A Detective with the Los Angeles Police Department and also the LAPD/NCIS liaison.|
|Kensi Blye||Daniela Ruah||NCIS Special Agent with the Office of Special Projects.|
|Eric Beale||Barrett Foa||Tech Operator with the Office of Special Projects.|
|Nell Jones||Renée Felice Smith||Tech Analyst for the Office of Special Projects.|
|Astrid||Abbie Cobb||A young girl with autism.|
|Mike Hoffman||Myk Watford|
|Oliver Mathers||Ian Alda||A Doctor.|
|George Toretto||Troy Winbush|
|Joseph R. Hepanta||Wayne Lopez||AKA "Construction Worker".|
|William LaMontley||Roy Werner||AKA "Rich Man".|
|Warren Blackstern||Paul Keith||AKA "Old Retiree".|
|Corey Danusville||David Magidoff||AKA "College Student".|
|Alton Ridgely||Robert Parks-Valletta||AKA "Waiter/Driver".|
|Mother 1||Ondrea J. Smith||Cameo. In real life, Ondrea J. Smith is the mother of LL Cool J who plays NCIS Special Agent Sam Hanna.|
|Mother 2||Julia O'Donnell||Cameo. In real life, Julia O'Donnell is the mother of Chris O'Donnell who plays NCIS Special Agent G. Callen.|
|Mother 3||Jeanne D. Olsen||Cameo. In real life, Jeanne D. Olsen is the mother of Eric Christian Olsen who plays LAPD Detective Marty Deeks.|
|Mother 4||Caterina Korn Broder||Cameo. In real life, Caterina Korn Broder is the mother of Daniela Ruah who plays NCIS Special Agent Kensi Blye.|