NCIS: The Fourth Season the top-rated investigative crime drama, continues the thrilling adventures of a cutting-edge crew of special agents who operate outside the government's chain of command. Led by Leroy Jethro Gibbs (Mark Harmon), a former Marine whose skills as an investigator are unmatched, this highly trained, tight-knit team travels the world investigating murder, espionage and terrorism. This 6-disc set includes all 24 action-packed episodes, along with top-notch, behind-the-scenes special features, from this critically acclaimed, one-of-a-kind series.