When the NCIS: LA team and the DEA uncover the cartel's plans to slyly transport billions of dollars' worth of cocaine from Colombia to the United States using a submarine, Callen and Sam must quickly locate the missing vessel. Meanwhile, Hetty is called to Washington in the aftermath of the controversial mission in Afghanistan.

When a news reporter announces the group responsible for the deadly explosion at a military-sponsored charity event, the team must investigate her claims and search for the attacker.

Sam is convinced that the theft of software for a new unmanned aerial vehicle is connected with the disappearance of the lead engineer's 10-year-old daughter, a girl Sam once provided protection detail for in Saudi Arabia.

When an undercover NCIS agent is suspected of working for the smuggler he's supposed to be investigating, the team takes him into custody to find his true intentions. Meanwhile, Kensi and Deeks discuss their personal relationship as Kensi returns to the field.

When the NCIS: Los Angeles team investigates a case involving a former marine who is being tracked down by members of al Qaeda for embezzling money from Iraq, Hetty assigns Nell to join Deeks in the field. Meanwhile, Eric is given a new partner in Ops.

After learning that Special Agent Kensi Blye disappeared and the Taliban may be he holding her captive, Hetty sends the NCIS: LA team to Afghanistan on a rescue mission.

The NCIS: LA team is called in to determine if the computer system that controls Russian missiles is at risk after Eric overhears his friend, a computer systems expert, being attacked during online game play. Meanwhile, Kensi is shocked when a familiar face from her past shows up in Afghanistan.

When an undercover agent is identified and executed by a local gang, the NCIS: Los Angeles team must locate the mole before other agents' lives are put in danger. Meanwhile, Granger begins to worry when Kensi disappears in Afghanistan.

Following an explosion at a fish market, the NCIS: LA team partners with an undercover DEA agent to determine if the incident is an act of terrorism or a botched drug smuggling deal. Meanwhile, in Afghanistan, Granger and Kensi investigate a helicopter crash that could be tied to their ongoing search for the infamous white ghost.

Sam and Callen head to Mexico to search for Tuhon, a retired assassin they encountered on their very first case together, now a suspect in the murder of a diplomat. Meanwhile, Nate and Deeks stay in Los Angeles to assist with the investigation.

When two private military contractors are murdered, the teams' investigation leads to a suspect who puts one of their own in serious danger. Meanwhile, Sam sets up Callen on a blind date.

While in Afghanistan, Kensi and Granger join the team on a joint case when a federal agent in Los Angeles tied to Hawala, an ancient system of money transfer, is murdered.

The NCIS: Los Angeles team searches for a motive when a senator's daughter is attacked. Meanwhile, Deeks and Nell partner up to help Sam and Callen bring the daughter to safety and Kensi receives the perfect holiday gift from one of her co-workers.

When a former Romanian Communist leader and suspected war criminal is discovered to be living in Los Angeles under a false identity, the NCIS: LA team must locate him before he disappears again.

Callen and Sam enlist the help of a Gurkha, an elite Nepali soldier specializing in knife fighting, to retrieve a missing thumb drive. Meanwhile, Kensi and Deeks struggle to find a balance in their partnership.

Kensi goes undercover as a nutritionist and Deeks poses as a new patient at a rehab center to investigate the death of a Navy officer.

When an antiterrorism device is stolen, the team must quickly find the suspect and the device before an attack is made against Los Angeles. Meanwhile, Hetty realizes the case is bringing her back to someone from her past.

The NCIS: LA team must notify Homeland Security when a murder investigation exposes a larger threat to a Los Angeles-based train.

Callen goes undercover at a prestigious high school after a 15-year-old hacker compromises terrorist missions.

Analyst Nell Jones joins the NCIS: LA team in the field when a former Navy officer's girlfriend is kidnapped in exchange for Navy intelligence. Meanwhile, Deeks unknowingly breaks one of Hetty's rules.

The NCIS: LA team finds themselves in danger while investigating a kidnapping case of a man claiming to be Callen's father.

The NCIS: LA team must find who compromised a classified vaccine project from a bio tech company. Meanwhile, Deeks struggles with his emotions upon returning to the field.

In an effort to help Sam and Deeks return to work, Hetty calls upon Operational Psychologist Nate Getz to help them cope with their traumatic experience. Meanwhile, the rest of the NCIS: LA team investigates the murder of a former Navy Admiral and a controversial journalist aboard a private jet.

While Sam and Deeks recover from traumatic torture that will have a lasting impact on their personal and professional relationships, lives are still in jeopardy as the NCIS: LA team searches for stolen nuclear weapons.