Ziva surprises Gibbs with a cryptic warning, prompting him to question why she remained underground for years while being presumed dead by family and friends, and what led to her return.With their lives in danger, Gibbs and Ziva’s rogue investigation takes an unexpected turn when a possible terrorist plot is revealed.After the body of a Marine Lieutenant is found hidden under an 18-wheeler, the NCIS team tracks the vehicle’s previous locations to pinpoint the crime scene and suspect. Sloane encourages the team to sit down and talk about Ziva’s recent reappearance.The NCIS team links a bizarre crime scene at Arlington National Cemetery to a string of attacks on homeless veterans.The team investigates a Marine Corporal after evidence suggests she murdered her neighbor while being treated for insomnia by a hypnotherapist.After a petty officer’s son is found murdered at his “welcome home from prison” party, evidence suggests Kasie’s lifelong best friend, Dante Brown, is the suspect.While investigating a Marine’s murder, the NCIS team uncovers a labyrinth of live-streaming spy cameras hidden in the rooms of a Virginia motel.The NCIS team investigates the murder of a musician in the Navy’s most elite band that performs at diplomatic events around the world.The team investigates a petty officer’s murder that was live-streamed on a popular gaming app. Also, Gibbs is asked to look after his 11-year-old neighbor, Phineas, when his mom must leave on a last-minute trip.The cases of the Naval Criminal Investigative Service's Washington, D.C. Major Case Response Team, led by Special Agent Leroy Jethro Gibbs.