Callen and Sam return for a 12th season of assignments, as the Naval Criminal Investigative Service encounter more and more threats. Chris O'Donnell and LL Cool J star.

Chris O’Donnell, who starred for 14 seasons as G. Callen on NCIS: Los Angeles, is moving to Music City for his next leading role on the Ryan Murphy/ABC spinoff, 9-1-1: Nashville, Deadline reports.

Chris O’Donnell, best known for playing Special Agent in Charge Grisha “G” Callen ... seasons of NCIS: Los Angeles. In today’s climate, few TV shows reach half of that season tally ...

Eric Christian Olsen and boss tease big 'reveal' in two-part episode 'NCIS: LA' boss on the season finale and the explosion that could spell disaster for the team -- EXCLUSIVE PHOTO 'NCIS ...