Operating independently, the Naval Criminal Investigative Service pursues the most difficult military-related crimes. Led by taciturn Special Agent Leroy Jethro Gibbs (Mark Harmon), the crack team delves into cases of murder, espionage, terrorism and more. Working with Gibbs are an ex-homicide cop (Michael Weatherly), a quirky forensic specialist (Pauley Perrette), a computer expert (Sean Murray) and a seasoned medical examiner (David McCallum).