NCIS: Los Angeles is a drama about the high-stakes world of the Office of Special Projects (OSP), a division of NCIS that is charged with apprehending dangerous and elusive criminals that pose a threat to the nation's security.
NCIS investigates the death of a Navy officer killed during an LAPD shootout with drug runners. Initially they think the officer was a hostage but when Callen and Sam find he has been picked up and dropped off daily by the drivers of the car and has been using his military clearance to send top secret satellite photos of a mounting anti-drug military mission to a drug cartel leader, they question his loyalty. Further investigation reveals that he was being forced to cooperate because his niece is being held hostage. When they learn the identity of the cartel leader, Callen and Sam go under cover posing as satellite experts, offering to replace the flow of secret information to him; their goal -- to get close enough to find the dead Navy officer's niece.
When three SEALs interrupt a drug deal, stealing the drug money -- two people end up dead, including an undercover LAPD officer. When NCIS watches the surveillance footage, Sam recognizes a former SEAL colleague, despite his mask, and the hunt is on to find the other team members and the evidence needed to convict them. Sam confronts his old friend, but gets little satisfaction. He's personally offended that his former brethren could violate their code so profoundly, particularly when one of their team turns up dead, having been killed in the initial robbery. In a surprise twist, the investigation leads NCIS to discover the undercover cop wasn't there to take down the drug dealers, but another LAPD officer who is leading a double life selling drugs. Using their skills as interrogators as well as their undercover acumen, Sam, Callen and the team are able to arrest the SEALs involved, as well as take down the dirty cop.
Sam, Callen and the team must work quickly to find a stolen Predator drone, still armed with a deadly missile. Using computer surveillance, Sam and Callen find the driver who transported the drone away from its landing sight. He’s an Islamic extremist who works for a computer software company, he kills himself as he’s being chased, but further investigation reveals he’s not a candidate to have mastered flying the drone. Eric and Dom use their computer tracking skills; they determine that video footage from the stolen drone was posted in a University classroom. Kensi goes undercover in the college class hoping to smoke out their suspect. She finds him, but he’s also killed before she can get any information from him. As they figure out who’s behind the theft, they realize the drone has been reactivated and is targeted to a local high school. Turning to the original drone “pilot,” they’re able to save the school and arrest the man behind the conspiracy.
Sam and Callen are charged with finding and bringing in Walton Flynn, a Citdential employee (private security group), who went crazy in Iraq and killed the wealthy Iraqi businessman he was supposed to be protecting. NCIS figures out that Flynn is romancing a high school friend of his in order to get her help and they go undercover to find out where he is without tipping to her that he's in trouble. Unfortunately, Citdential has their own agenda and seem to be hell-bent on taking him down before NCIS can take him in. Turns out, he has proof that the head of Citdential killed the Iraqi businessman, making him the scapegoat. When they find capture Flynn, Callen decides to let him go -- he's not guilty of anything and Callen knows Citdential’s reach would put Flynn in danger.
A scientist working on a highly classified DARPA project is killed by a sniper while jet-skiing on the beach. As NCIS investigates, Sam and Callen find his business partner bludgeoned to death in their offices. As the team compares evidence from both crime scenes, Leon Vance arrives, announcing the sniper is Lee Wuan Kai, a highly skilled assassin he’s crossed paths with before; once nearly killing him. Vance is surprised when Lee Wuan Kai calls him and tells him she didn't kill the business partner, she takes pride in her work and doesn't want that messy kill attributed to her. As Kensi, Nate and Dom investigate the death of the business partner, Vance puts pressure on Sam and Callen to not to let Lee Wuan Kai escape justice this time.
When a Marine, Brandon Valdivia, is thrown off the patio roof of a trendy downtown hotel, NCIS must unravel several mysteries around his death. Examining Valdivia's financial history, Kensi and Dom determine that he and his co-worker, Alex Walder, were involved in a counterfeit money scheme and Secret Service Agent Natalie Giordano arrives to assist with the case as it connects to a counterfeit distribution network she's been tracking. She's also hoping to make a more personal connection with Callen but he's not going to violate his "no law enforcement" policy when it comes to dating. NCIS tracks down Alex Walder and learns that Valdivia and Walder were making counterfeit bills with plates they found when they were stationed in Bagdad. Walder believes that their printer killed Valdivia and is after him so Kensi and Callen go undercover to collect evidence on the printer. When the "buyer" of the bills shows up, they're shocked to discover it’s the Marines' Sergeant: he killed Valdivia. His plan was to ship the fakes to Iran for distribution in the military, keeping the real money that was being sent for him.
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 away, the NCIS team searches for 4 missing anti-tank missiles that are in the hands of a racist militia group. Renko (from Legend), has brought them their best lead, a Marine named Private Reilly, whom they arrest. Callen goes undercover as another detainee, hoping to bond with Reilly and gather information that might lead them to the location of the missiles. NCIS stages a raid on their jail transport truck and Callen and Reilly "escape". Reilly offers Callen a place to hide until things cool down. Thinking they’re getting access to Reilly’s contact, NCIS is stunned and somewhat unprepared when they learn Callen has gained access to the main camp of the militia group and the leader is incredibly suspicious. Sam jumps in to protect Callen just as they're about to shoot him, but now Sam and Callen are prisoners. Kensi figures out how to communicate with Callen and he suggests they be inspired by the trickery of the WWII British intelligence officer, Maskelyne. The team puts on an impressive show that makes the militia group believe they're surrounded and NCIS arrests the leaders and finds the missiles.
Callen, Sam and the team investigate a top Naval Engineer's murder and get unexpected help when Director Vance sends Abby to Los Angeles. Abby has a theory that a number of seemingly unconnected murders have been perpetrated by the same killer, someone she has dubbed the "Phantom" because he leaves behind no trace evidence. While Sam and Callen investigate their best suspect, the engineer's bitter wife, Abby examines the crime scene. The 'negative' footprint at the scene gives Abby her best clue, the killer is wearing a special hazmat suit which picked up dust, leaving the footprint and explaining why there is no forensic evidence. While they're waiting on information about the suit, Eric and Abby go out to a Hollywood Goth club, and everyone is stunned when Abby is kidnapped. The investigation quickly shifts to find Abby. Nate suspects the killer will keep Abby alive to gain her admiration for his "work" but time is limited. When the team find where the "Phantom" is keeping Abby, they must stage a daring rescue because they know he has booby-trapped his lair.
It's Christmas time and while Hetty decorates the NCIS:LA palm "Christmas tree", Callen and the team investigate the death of a Marine whose cell phone exploded in his ear. The investigation leads them to three of the victim's fellow Marines. They all worked with an EOD unit (Explosive Ordnance Disposal) in Iraq and all were discharged after their convoy was bombed. When they find two other members of the team were also targets of hidden bombs, the team focuses on a fourth Marine, so disfigured in the incident in Iraq, he won't return to his family. However, he provides a missing piece of the puzzle and refocuses the investigation on the actual killer.
After a brief altercation at a strip club, a young black man drives his truck into the club, narrowly missing Katya, a stripper, but killing a Petty Officer. When the NCIS: LA team identifies the driver of the truck as a Sudanese refugee, Sam turns to a teenager named Moe for information about the driver and the man he was with. Sam sponsored Moe to come to America. Unbeknownst to Moe, Sam killed Moe’s father, who was part of the Sudanese rebellion. Moe says he knew the driver, and identifies the man he was with at the club as Safar; Sam expresses concern that Moe is hanging out with the wrong people, but Moe enjoys being with people from his homeland. The NCIS:LA team identifies Safar as a Libyan born terrorist and they speculate that he snuck into the country to recruit the "lost boys of the Sudan" to return to their country and join the unrest. Since Safar was a regular at the strip club, they turn to Katya for further information, only to discover the owner of the strip club has the place wired, and uses the recordings to bribe his customers for money or information. Using the recordings they set a trap and capture Safar. It's a bittersweet moment, as they know the CIA will try to "turn" Safar. Also Safar has already poisoned Moe against Sam by telling Moe about his father’s death. Sam races to find Moe, but he’s too late to stop Moe from leaving the country to join Safar's terrorist training group.
Also, the death of a former colleague of Hetty's has her worried that her team is too married to their jobs and she sets rules to limit their workload in order to encourage them to build a life outside the office.
The murder of a cab driver just hours after he sent an email to an old alias of Callen's triggers NCIS: LA to reopen an old case. Four years earlier, Callen spent 6 months in deep cover as a corrupt MP: his goal was to get close to 3 Marines who stole $5 million and collect evidence to convict them, as well as recover the money. They convicted all 3 Marines, two of whom cooperated, however, NCIS didn't find the money because it had been moved and the felons didn't know where. The murdered cab driver was one of the conspirators, recently released from prison and he emailed Callen for his help because he'd found the money. Kensi interviews the one thief still in prison (he didn't cooperate) and finds herself being interested in his lawyer. Meanwhile, Callen resumes his past undercover role to track down the third conspirator, Jon Donnelly. Sam tracks Callen, worried that he's going "lone wolf" on him. Sam isn't pleased to discover Callen had a romantic relationship with Donnelly's sister and she has a 4 year old son (who turns out not to be Callen’s). Through the sister, Callen finds Donnelly but he's murdered before Callen can speak to him. They realize the third man still in prison must be the connection to missing money and the murders, but when he's also killed, they figure out his lawyer stole the money and is getting rid of all the evidence.
Everyone gets an "Agent Needs Assistance" page from Dom during their annual ethics meeting. Using the GPS on Dom's car, they race to its location only to find LAPD already at the scene. The car is filled with blood, a seemingly fatal injury, but there is no body, leaving hope that Dom is still alive. Callen leads the team to investigate Dom's kidnapping. Ultimately they identify and bring down the kidnappers, but they were only hired guns and had already traded Dom for money. Each of the agents has a different response to his disappearance, but Sam takes it hardest, refusing to believe he isn't coming back.
A warehouse with five dead bodies, two of whom were apparently Marines, draws the attention of NCIS. The "Marines" were wearing authentic uniforms, but weren't Marines, so NCIS is intending to oversee the investigation to make sure there is no military connection, however, when the cause of death is determined to be Botulinum poisoning, NCIS:LA takes on the case because Botulinum is a deadly neurotoxin and bio-weapon. Sam and Callen pursue their first lead, an elderly woman suffering from Alzheimer's -- turns out she was a military chemist and she was approached by people she thought were Marines to help them isolate, purify and weaponize the toxin. Though her disease makes her an unreliable witness, the rote memory of her job has not been destroyed and she successfully produces enough biotoxin to kill millions of people. Callen recognized one of the dead bodies as a former security guard for Dallas (from Breach, the strip club owner with high-powered connections) and through him, they discover that a weapons dealer named "The Dutchman" is holding an auction for the poison. Sam goes undercover as an interested buyer, and discovers there's going to be a demonstration at the Beverly Center. Callen and Kensi race to the location and manage to thwart the attack.
In Iraq, an Islamic terrorist group steals a truck with $5 million dollars of U.S. cash and NCIS: LA tracks the money back to the U.S. where they learn the money has been stolen to hire an accomplished bank robber to rob a local bank. Further investigation suggests that the bank robbery is intended as a ruse to allow a bank employee to transfer $100 million of the terrorist’s money that has been frozen by the government to an offshore bank. During the robbery, Kensi gets shot and though Sam is able to kill a couple of the robbers, the bank employee gets away. Nothing is as it seems but Callen and Sam are able to reclaim the money and arrest the inside man.
NCIS:LA has to investigate the apparent suicide of a Naval Officer named Calvin Lee, who jumped off a freeway overpass. Traffic camera footage makes it clear that he was alone when he jumped, but because Calvin was the XO of a high-tech submarine, Sam and Callen must investigate him to be absolutely sure Calvin didn't compromise anything before he died.
Calvin's parents immigrated to the U.S. from China in order to escape the one-child laws in China. They have an older daughter to whom they no longer speak. Calvin was apparently engaged to a Chinese national, but the marriage was arranged by his parents and Calvin is gay. When they get to Calvin's boyfriend's apartment, they find him murdered, making them suspect it's a case of murder-suicide. However, evidence leads them to a Chinese hit-man, apparently hired by Calvin's fiancée. They also find the device Calvin threw over the bridge before he jumped. Turns out the device is a hard drive cloner devised by the Chinese government, leading them to conclude Calvin was a spy for China. They question his parents further and uncover that though Calvin was born and groomed to be the perfect sleeper agent, he didn't want to betray the U.S. and committed suicide to avoid being forced to.
NCIS: LA investigates the death of James Rush, a young Naval officer killed when his car suddenly explodes in an illegal street race. Initially it looks like a rival street racer sabotaged his car, however, NCIS: LA discovers the rival was Rush’s girlfriend who raced under a male persona. She very upset about his death and an unlikely candidate for his murderer. Rush left behind a brother and sister who have been trying to keep the family business, a garage, alive; their brother’s death has ruined them emotionally and financially. Kensi and Sam then discover that Rush had stolen two advanced lithium-ion battery systems from his military unit. It seems that Rush had been working on this top secret power-boosting device and “borrowed” the equipment to road test it. The second device is missing and now Kensi and Sam must not only try to solve Rush’s murder, but also recover the second system.
Also, Callen must go to traffic school because of a speeding ticket, but he keeps getting pulled away to help out with the case.
When Marine Gunnery Sergeant Wendall Dobbs is gunned down in the streets by a gang wielding AK-47's, NCIS: LA suspects Dobbs could be involved with illegally importing automatic weapons into the country and supplying them to local gangs. Investigation into Dobbs life reveals that he is above suspicious and traded in his combat post for an administrative position in order to mentor his younger brother, Darryl, who has been hanging out with a gang. Sam goes undercover to pose as a cousin and Darryl introduces him around. As Sam gets involved in gang business, Callen and Kensi investigate how the guns were getting in to the country. Turns out, the guns were cheap knockoffs that came from an outfit in Florida, and though they were used to kill Dobbs, they weren't the reason for his death. In fact, Dobbs had stumbled on a heroin smuggling scheme whereby gang members stationed with the military in Afghanistan were hiding heroin in the side panels of military Humvees being shipped back to the US.
When Daniel Zuna, a Marine on leave, bleeds to death outside a club, NCIS: LA's first stop is to investigate the Mixed Martial Arts gym where he spends most of his off-duty time. Kensi goes in posing as Zuna's new girlfriend. She meets several members of the gym's team, most of whom were Marines who served with Zuna in Iraq. After interviewing Zuna's former CO, it seems likely that Zuna's murder could be related to something that happened in Iraq. Sam goes in undercover as an MMA fighter in order to get an inside line on this history, but is quickly targeted by another fighter who feels Sam is edging him off the team. Turns out, the fighter is LAPD officer Marty Deeks, who has been working undercover in they gym because it's linked to a major drug cartel. Reluctantly, Sam joins forces with Deeks to work both the drug case as well as the murder, in case they’re related. When another Marine from Zuna’s squad, is murdered, it’s clear they need to learn the truth of what happened in Iraq in order to solve the case.
A navy Lieutenant dies when he rolls off a cliff along Mulholland Blvd. Turns out, he was shot before he crashed the car and the car belonged to Aubrey Darva, the socialite daughter of a wealthy real estate investor. LAPD Officer Deeks is on loan to NCIS: LA as a temp in Dom's continued absence, however, he proves to be of little help as a liaison officer to LAPD, as his fellow cops don't really like him. Their first stop is to Aubrey Darva's house; Aubrey's father has just flown in from NYC and discovers she's gone missing. When Sam and Callen finally find Aubrey, they learn that the Lieutenant was with her the night before but disappeared in the middle of the night. Kensi stays with Aubrey for her protection and figures out that the Lieutenant was killed in Aubrey's house. Turns out, he was killed when he discovered a known terrorist was staying at the Darvas' house. Kensi finds herself in the same position but manages, with the help of Mr. Darva, to save herself and the Darva family.
The NCIS team races to save one of their own when they receive video evidence of Special Agent Dominic Vail being held hostage months after he was kidnapped.
An attack of a private plane immediately after it lands, turns out to be a terrorist takedown of the secret army transfer of terrorist, Ala A Din Keshwar. NCIS: LA gets called in because Keshwar is the man Dom's captors wanted released. NCIS didn't know the Army had him in custody, much less that they were transferring him. Tempers run high in a jurisdictional war with Army Major Rick Medina, as they try to find Keshwar before he escapes the country. They track down the van Keshwar left the airport in, and Medina has his men charge it, against Callen's orders not to. As Callen predicted, the van was a trap with a suicide bomber driver, who blew up the van and the men who got close to it. Using NCIS: LA’s tracking resources, Sam pushes to find Moe, the Sudanese "lost boy" he sponsored to get in the country; Moe has knowledge of the organization that freed Keshwar. Sam finds Moe, restores Moe’s trust and learns Moe got back into the country on a Turkish ship. Callen suspects that Keshwar will use the same route to disappear and they race to the port. Improvising a quick undercover ruse, Callen and Kensi get close to the ship, however, Medina shows up at the last minute, nearly blowing their operation. Turns out Medina sold out for money and was trying to help Keshwar escape.
When Callen's cover is blown, he's forced to cut all ties with NCIS. The man behind exposing Callen is a mysterious information broker, Eugene Keelson, who claims he has collected data on Callen that will reveal his past. Keelson's willing to trade that information if Callen performs one favor for him: deliver a flash drive to a group of Bulgarians. Callen does the delivery but the Bulgarians, believing he's Keelson, try to kill him. Meanwhile, Hetty has Eric shut down all of NCIS's electronics as Keelson has sent a Trojan horse infecting all of Callen's files. Torn between learning more about his hidden background and his responsibilities as an NCIS agent, Callen knows he can't work the case. The flash drive has information about a hit the Bulgarians are meant to perform, and while Sam and the team work to prevent the hit, Eric discovers the entire NCIS operation has been infiltrated by Keelson. This forces Hetty to bring Callen back in. Callen sets up a meet with Keelson to buy back all of NCIS' sensitive information. At the meet, Keelson sends one of the thwarted Bulgarians, knowing either Callen or the Bulgarian will be killed. Callen survives, finds Keelson, but ends up killing him in self-defense, thereby losing his connection to the one person who knows about Callen's past…Until, Eric realizes there's a house where Keelson may have stored this information. Story continues in season finale, "Callen, G."
Callen races against a ruthless adversary to locate a woman who knows the whereabouts of a forgotten fortune earmarked to fund a new war in the Middle East - and also holds the tantalizing key to his unknown past.