NCIS (Naval Criminal Investigative Service) focuses on the sometimes complex and always amusing dynamics of a team forced to work together in high-stress situations. NCIS Special Agent Leroy Jethro Gibbs (Mark Harmon), a former Marine gunnery sergeant, whose skills as an investigator are unmatched, formerly led this troupe of colorful personalities. Gibbs, a man of few words, only needs a look to explain it all. The team includes NCIS Special Agent Anthony DiNozzo (Michael Weatherly), an ex-homicide detective who may come off as the world's oldest frat boy, but whose instincts in the field are unparalleled; forensic specialist Abby Sciuto (Pauley Perrette), a talented scientist whose dark wit matches her Goth style and eclectic tastes, NCIS Special Agent Timothy McGee (Sean Murray), an MIT graduate whose brilliance with computers far overshadows his insecurities in the field; and Ziva David (Cote de Pablo), a former Moussad agent who shares a bond with Gibbs over the death of his arch nemesis, a terrorist who killed former NCIS Special Agent Kate Todd. Assisting the team is medical examiner Dr. Donald "Ducky" Mallard (David McCallum), who knows it all because he's seen it all, and he's not afraid to let you know. Rounding out the team is NCIS director Jennifer Shepard (Lauren Holly) who has a romantic history with Gibbs. From murder and espionage to terrorism and stolen submarines, these special agents travel the globe to investigate all crimes with Navy or Marine Corps ties. Season 4 aired from 2006-07 on CBS.