NCIS (Naval Criminal Investigative Service) is an action drama, about a team of special agents whose mission is to investigate any crime that has a shred of evidence connected to Navy and Marine Corps personnel, regardless of rank or position. Leading this team that operates outside of the military chain of command is NCIS Special Agent Leroy Jethro Gibbs (Mark Harmon), a highly-skilled investigator and interrogator who is smart, tough and willing to bend the rules to get the job done. Working under Gibbs is Special Agent Anthony DiNozzo (Michael Weatherly) a former Homicide Detective who has instincts that come only from working on the streets. Joining them are Agent Kate Todd (Sasha Alexander), a beautiful, tough former Secret Service Agent who has gone head-to-head with Gibbs in the past. She is killed on the last episode of season 2. Kate is replaced by Officer Ziva David (Cote de Pablo) a beautiful Mossad Agent. In season 2 there is a new member in Gibbs his team Special Agent Timothy McGee (Sean Murray), a graduate of MIT whose computer skills earned him a spot on Gibb's team as a probationary Field Agent.
Then there is forensics specialist Abby Sciuto (Pauley Perrette), a gifted scientist whose dark wit matches her goth-style hair and clothes. Assisting the team is medical examiner Dr. Donald "Ducky" Mallard (David McCallum), who knows it all because he's seen it all: from murder and espionage to terrorism and stolen submarines. The Director of NCIS is Leon Vance (Rocky Carroll), who is the replacement for Director Jenny Shepard (Lauren Holly), who is killed in the special two-hour finale of season 5, while protecting Gibbs from a past European assignment the two shared.
These Special Agents travel the globe to investigate all crimes with Navy or Marine Corps ties.