Former FBI Agent Tobias Fornell pleads with Gibbs to do whatever is necessary to take down drug dealers and suppliers in the area after his daughter, Emily Fornell, is hospitalized from an opiate overdose. Gibbs is haunted by the personal aspects of the case and his history with vigilante justice.

The NCIS team investigates the murder of a Marine Sergeant in the States who was hailed as a war hero for his efforts overseas. Also, Gibbs turns to Doctor Grace Confalone for advice after he uncharacteristically unravels and abandons his team at a crime scene investigation.

After NCIS finds a secret government bank account that's funding a nationwide network of vigilante justice, the team must determine who is acting as judge and jury.

After entering cold case DNA into the system, Kasie solves a 30-year-old murder case, but a loophole in the legal system may set the suspect free. Also, McGee visits an elite technology company in Silicon Valley that is offering him a highly paid position.

NCIS investigates the murder of a Marine Major believed to have been killed in the 9/11 attack on the Pentagon after human remains are discovered at a construction site. A personal history with the victim drives Gibbs to solve her crime.

Following an active shooter lockdown at a naval hospital, the NCIS team searches for a suspect who fled the scene. Also, someone from Sloane's past was inside the hospital and is a key witness in the case.

Torres relies on his team's investigative skills after he wakes up on a dilapidated fishing boat, covered in blood and unable to remember the last 12 hours.

Director Vance is notified by the Pentagon that the nuclear submarine Gibbs and Bishop are aboard to conduct a murder investigation has gone radio silent.

Jimmy is torn between family and work after his father-in-law, Ed, asks him to tamper with evidence from NCIS' current murder investigation. Also, Ed's poker buddy, Anthony DiNozzo, Sr., offers to help with the case.

The NCIS team investigates a man overboard fatality from a Navy destroyer at sea. Also, Torres is frustrated with Vance's assignment to mentor three high school students.

McGee reluctantly visits his high school after the unique computer password he used as a teenager is linked to the murder of a department of defense contractor. The case escalates when an intruder breaks into McGee's home in an attempt to steal his archaic high school computer.

After a malnourished and confused 9-year-old is found hiding in a storage unit, NCIS reopens an old missing persons case when the girl is believed to be the daughter of a Navy recruit who disappeared 10 years ago. Also, Bishop discovers notes that Special Agent Ziva David kept on the case long after NCIS officially stopped investigating.

An old family friend, Army Corporal John Sydney, beseeches Gibbs to join him on a road trip to search for a missing military I.D. bracelet. Also, a Navy Lieutenant in NCIS protective custody is poisoned by an infamous drug dealer.

United States Secretary of Defense Wynn Crawford shuts down Gibbs' murder investigation and demands that Special Agents McGee and Torres be arrested for their actions in the case.

The team's holiday plans are put on hold when the murder investigation of a Navy veteran includes the discovery of a newborn baby who has no identification and no apparent ties to a family.

When the lead suspect of an unsolved and high-profile robbery case is released from prison, the NCIS team resumes their investigation with an undercover stakeout.

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. Also, Kasie leaves the lab and accompanies Torres into the field to process additional forensic evidence.

After a mural by a street artist and activist is stolen, the NCIS investigation leads to a conspiracy regarding a Navy contractor and the safety of ocean mammals. Also, Bishop shares a special connection with the street artist.

After NCIS arrives at a Halloween crime scene, Torres recognizes the victim as a friend from federal law enforcement training. Also, Jimmy thinks his lab is haunted by ghosts after objects keep mysteriously moving.

After a 50-year-old tape recording left by a murder victim is found, the NCIS team tries to exonerate Ray Jennings, the Marine serving a life sentence for the crime.

Gibbs' quiet vacation at his remote cabin is interrupted by a surprise visit from Tobias Fornell and Navy Captain Phillip Brooks, as well as a call from NCIS asking for his help locating a robber hiding in the woods near him.

One of the NCIS agents is starstruck after the team investigates an explosion outside the home of Navy Petty Officer First Class Todd Nicholas and his wife, popular reality TV star Sheba Nicholas. Also, Vance continues physical therapy for the injuries sustained when he was held hostage.

After a Navy lieutenant is found murdered in his hot tub, the team interviews several families in the victim's peculiar neighborhood. Also, Torres must face the consequences after a volatile night out with Palmer.

One month after Director Vance was kidnapped, Gibbs is assigned the role of acting director in his absence while the team searches worldwide for his whereabouts.