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 Owne 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.