Red Part 1 (or "Red") is the 18th episode of NCIS: Los Angeles Season 4 as well as the 90th episode of the entire NCIS: Los Angeles series.
OSP investigate when a murder weapon that was used to kill an arms dealer in Los Angeles matches one used to kill a United States Marine in Idaho. As Callen and Sam head to Idaho to meet with NCIS Assistant Director Owen Granger and join the investigation led by the NCIS: Red Team, a group of agents who live and work together in two mobile units as they solve crimes in various locations in America and all over the world, Kensi and Deeks work the case from OSP Headquarters in Los Angeles with the team soon finding evidence suggesting that a terrorist attack that could take place, one similar to that of September 11.
- Kensi gives Deeks the mysterious Box she recieved in Kill House (episode).
- Callen and Sam head to Idaho where they reunite with Granger and also meet their counterparts- the NCIS Red Team led by Paris Summerskill.
- NCIS Special Agents Paris Summerskill, Dave Flynn and Claire Keats along with former Agent Roy Haines and Tech Assistant Kai Ashe are all introduced for the first time.
|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.|
|Owen Granger||Miguel Ferrer||Assistant Director for NCIS.|
|Paris Summerskill||Kim Raver||NCIS Special Agent and Agent in charge of the NCIS: Red Team.|
|Roy Haines||John Corbett||Former NCIS Special Agent.|
|Dave Flynn||Scott Grimes||NCIS Special Agent with the NCIS: Red Team and also the team's forensic scientist.|
|Claire Keats||Gillian Alexy||NCIS Special Agent with the NCIS: Red Team.|
|Kai Ashe||Edwin Hodge||Tech Assistant with the NCIS: Red Team.|
|Danny Gallagher||Kenneth Mitchell||NCIS Special Agent with the Red Team.|
|Ari Sayed||Omid Abtahi||A terrorist.|
|Edward Tyler||Sterling Sulieman||Gunnery Sergeant in the United States Marine Corps.|
|Robert Spears||Jonathan Oldham||Main suspect.|
|Foxy Lady||Vanessa Vander Pluym|
|Friend||Brittany-Elle Benson||Uncredited role.|
|Brett||Lachlan Buchanan||Uncredited role.|
|Bouncer (Red Part 1)||Victor E. Chan||Uncredited role.|
|Terrorist 1||Anthony Martins||Uncredited role.|
|Rachmed Santoso||Ayman Samman||Arms dealer. Uncredited role.|
|Daisy||Jessalyn Wanlim||Uncredited role.|