
Naval Criminal Investigative Service Special Agent Leroy Jethro Gibbs leads a group of colorful personalities in investigating crimes -- ranging from murder and espionage to terrorism -- that have evidence connected to Navy and Marine Corps personnel. The team includes MIT graduate Timothy McGee, Ellie Bishop, who specializes in international threat assessment, charismatic and unpredictable Nick Torres, and forensic psychologist Jack Sloane. Dr. Donald "Ducky" Mallard brings his vast experience in forensics into play to help solve cases.
When a dead thief is found in a Marine's home, the NCIS team finds the calling card of a terror group the Department of Defense had been tracking.
After NCIS arrives at a Halloween crime scene, Torres recognizes the victim as a friend from federal law enforcement training; Jimmy thinks his lab is haunted by ghosts after objects keep mysteriously moving.
A street artist's mural is stolen, and the investigation leads to a conspiracy regarding a Navy contractor and the safety of ocean mammals; Bishop shares a special connection with the street artist.
McGee and Bishop travel to Afghanistan after a murder case in the states is linked to a string of soldiers killed by friendly fire overseas; Kasie leaves the lab and accompanies Torres into the field to process additional forensic evidence.