The long-running television series, NCIS watched by fans around the world is based on a composite of crimes investigated by the real NCIS. The United States Naval Criminal Investigative Service (NCIS) Headquarters is located in the Russell-Know Building on Marine Corps Base Quantico. NCIS NCIS Headquarters serves at the center operations for all NCIS missions overseeing all 191 locations in 41 countries. NCIS is the civilian federal law enforcement agency responsible for investigating felony crime, preventing terrorism and protecting secrets for the Navy and Marine Corps.  In addition to activities shown in the TV show, NCIS mission includes economic crimes, counterterrorism, counterintelligence, cyber threats, crime reduction, etc.