Four months after being shot, Agent Callen returns to the Office of Special Projects and joins the Los Angeles team on a kidnapping case.
A case involving the murder of a drug dealer turns personal for Special Agent Sam Hanna when he discovers his former Navy Seal comrades are involved.
The team is assigned to track down a missing unmanned aerial vehicle (UAV) after it is compromised during a training exercise, killing a Marine before it disappears.
When an Iraqi businessman is murdered, the team searches for the former Marine who was hired to protect him.
Following a murder, the secrets to classified software are thought to be lost until NCIS uncovers a suspect from Vance's past.
The NCIS team must find a motive when they discover the body of a Marine who had been living a double life as a wealthy bachelor.
Following the murder of a Russian woman, the NCIS team uncovers evidence that answers who and why Callen was shot six months ago.
While Hetty is at a Senate hearing in Washington, D.C., a murder investigation leads the team to stolen missiles and a dangerous militia group.
Forensic scientist Abby Sciuto (Pauley Perrette) joins the team when a murder case resembles the pattern of a serial killer she has been tracking.
The NCIS team races to solve the murder of a Marine by an exploding cell phone and to find the remaining men of his former EOD (explosive ordnance disposal) unit before another deadly explosion kills someone else.
A petty officer's death leads the team to a teenager in Sam's life; Hetty is concerned about the effect that the workload has on the team.
The murder of a recently released convict forces Callen to go under cover with an old alias.
After receiving a page that an agent needs assistance, the team rushes to a crime scene and learns that one of its own is in peril.
A crime scene poses a security risk when the team discovers the location was used to create a deadly toxin that is now missing.
While opening a safety deposit box at a local bank, NCIS Special Agent Kensi Blye is shot after three armed assailants enter and hold everyone in the building hostage.
The team investigates the death of a lieutenant, which appears to be suicide; Nate joins Kensi in the field.
When a sailor dies in an underground street race, the team determines that his car, which contained confidential Navy equipment, had been sabotaged; Callen must go to traffic school.
When a Marine is killed in a drive-by shooting, the team fears his younger brother may also be targeted.
When an undercover operation has the NCIS team investigating a MMA gym and its fighters, Sam Hanna is tasked with donning gloves and entering the cage for a one-on-one fight.
LAPD liaison Marty Deeks helps the team find an infamous socialite connected to a Navy officer's murder.
The team races to save one of its own after receiving video evidence of Dominic Vail being held hostage.
The NCIS team is on the hunt for a terrorist who escaped Army custody during a secretive transfer in Los Angeles.
After Callen's cover is blown and compromises the unit, the NCIS team races to find out who is behind the security breach.