Callan returns to duty after his shooting. A kidnapped Commander in Naval Intelligence dies during a shootout between his captors and the LAPD.

At a home in Malibu, California, three masked intruders steal a large sum of money; two men die; the LAPD requests help from the NCIS; Director Vance refers the case to the OSP in Los Angeles. Sam and the gang figure it out and work it out.

During a training exercise involving an armed drone and ground forces at Camp Pendleton, the drone changes course, launches a missile, kills a Marine, and disappears; the Callen team investigate, find the bad guys, and nail the head man.

A discharged Marine, now an employee of a security firm working for the US government, returns to LA from Baghdad, accused of having killed an Iraqi; Vance tasks the Callen team to find the Marine; they find him and figure out everything.

An electronics engineer (who defected from North Korea) dies of a gunshot; his firm just won a contract with the DoD to create a communication system for the Marine Corps; Callen and company investigate; they find and lose the assassin.

A Marine corporal from Camp Pendleton dies by falling from the roof of a hotel in Los Angeles; while investigating, the Callen team find a connection with counterfeiting; the Secret Service joins; the feds find and catch all the bad guys.

An unident young woman dies while making a video recording; the LAPD contacts the NCIS; while investigating, Callen and company find connections and coincidences going back 10 years to Moscow; after hide-and-seek the team cuff the bad guy.

A lance corporal in the Marine Corps Reserve dies of garroting; he was an informant about the theft of six missiles from the Marine Corps Base; while investigating, G and Sam go undercover; with help they get the bad guys and the missiles.

A Navy Chief Petty Officer, who worked on classified technology, is murdered. The team search for a killer with a particular MO.

A discharged Marine, who served as a staff sergeant in Iraq with an EOD unit, dies of a detonation of an explosive device in his cellphone; the Callen team investigate, find three fellow EOD Marines, solve the case, and catch the bad guy.

An impaired driver crashes a stolen car into a strip joint; the driver dies, as does a patron, a Navy petty officer; the Callen team investigate; G finds a body inside a refrigerator, and Sam gets a promising lead; they grab the bad guy.

A disguised gunman executes a taxi driver; the cabby was a former Navy systems technician and petty officer third-class; G is involved as a former alias in an old case; the Callen team investigate; they find the pieces and the bad guy.

Dom, using his cellphone, broadcasts messages seeking help; they respond; they find Dom's car, unoccupied and bloody, but there's no sign of him. Eric provides leads, which they trace, and they make some progress, but Dom remains missing.

A TV reporter accompanies a group of ATF agents on a raid of suspected gunrunners; on the deck they find the bodies of five civilian men, already dead, two of whom (career criminals) wear authentic uniforms of the US Marine Corps and bear counterfeit ID cards; Director Vance orders the Callen team to investigate. G and Sam find dead birds and squirrels; Eric and Kensi find telephone traces and a street address, which allow the team to meet Esther, a sweet elderly retired researcher in biological warfare, who now suffers from Alzheimer's disease. Esther tells about her recent work, believing that she serves her country; she tells also about her two "Marine" drivers, who take her to and from a lab, where she recently isolated a protein responsible for botulism. The team find someone who provides answers; Sam goes undercover and attends a party and breaks it up; G musters a number of helpers, who catch the bad guys; G and Kensi go shopping; G and Sam take matters in hand.

Last month in Baghdad during an ambush of a convoy, one US Marine died, and six sustained injuries, then a robbery took $5M of US funds; now a clue leads to a connection in the LA area; the Callen team get the cash, the bad guys, and more.

A driver spots the body of a Naval officer, hanging from a highway overpass; the victim was a submariner, nuclear physicist, lieutenant commander, and XO of a fast-attack boat; Callen and company solve the puzzle and grab the last bad guy.

During a drag race a Navy yeoman dies in a crash; Callen and company investigate; the victim worked on something highly classified. Sam suggests the possibility of homicide. The team work on the puzzle; Kensi finds the last piece.

While a Marine gunnery sergeant, Wendell, walks down a sidewalk by night in Los Angeles, two cars roll by, and four gunmen with AK-47 machine guns shoot him to death; Callen and company investigate; G and Sam visit Wendell's father, learn about James, a younger son, and find themselves in a hail of gunfire; Sam says that the weapons and the ammo are the same as what killed Wendell. Eric finds two links to the same black street gang; G and Sam check out James's place of employment, and they find him inside Wendell's pad; while Nate spends time with James, the three musketeers check out other angles, and a gang battle breaks out and kills four; then James makes an amazing confession to G; a gang rampage goes down by night in a turf war over drugs; Sam and James attend a conference with several local businessmen; G takes a ride with three of them, and they do a job at a worksite; another gunfight breaks out and ends, and the team learn the remaining answers.

A Marine is found in an alleyway bleeding out from his eyes, ears and mouth. The team must determine whether he was the victim of a bio-agent and who killed him.

At 02:15 one morning a Navy lieutenant (j.g.), Brian, with two gunshot wounds, in a car not his own, drives into a canyon from Mulholland Drive in Los Angeles, then dies; Callen and company, including Deeks, investigate; Deeks has a couple of awkward moments; the team pick up several clues about the circumstances of the preceding night, including Aubrey, a young socialite woman. Kensi and Deeks speak with Aubrey's stepfather. G, Kensi, and Deeks go nightclubbing; Kensi discovers an alive missing girl, and she says that a victim just became a suspect; the team meet several interesting people; Kensi decks one and cuffs him, and G pops another one; the team escort away Aubrey, who gives Kensi much useful information. Kensi and Aubrey go to the latter's home, where Kensi sees more clues, more people, and a part of a solution; Aubrey leaves, Kensi gets into trouble, and G, Sam, and Deeks ride to the rescue. The team finish putting together the pieces about the death and more.

Dom shows up as a prisoner on a jihadist website; the OSP team swing into action; Sam sees his friend Moe; a runner provides a lead to a wealthy source of funds for terrorism; Dom escapes with help, and Sam finds him but not soon enough.

At the Van Nuys Airport, while two boys watch and record flight ops, a bizjet arrives with a prisoner, a shoot-out occurs, and the prisoner (the leader of the TaJ) vanishes; G and company get him, and G figures out the rest of the story.

While undercover G realizes that someone tails him, G chases him and watches while the tail dies; G becomes a ghost; two weird phone calls lead to major confrontations with Bulgarians and computer problems. G and the team walk away safely.

While G, Sam, and Kensi visit Keelson's computer center and physical records, the computer files self-destruct, and the premises ignite and burn; however, they rescue several documents, which include a list of G's 37 foster homes and orphanages plus five more addresses, which he does not recognize. The team, tracing clues, find a birth certificate for Amy Callen, now known as Amy Taylor; Hetty sends Sam and Kensi to Amy's place but chats up G; Eric gives G some data; Sam and Kensi find a tossed pad with nobody at home; G pursues a lead and finds a trashed home, the infamous Trent Kort, of the CIA, with whom G previously worked, and who shows him the body of a contact killed by bizarre means. Eric gives clues to G, who traces a lead to Amy, who as a teenager said that she had a brother; while pursuing a van, G runs into trouble, but he finds Amy, who's truly Hannah Lawson, but who tells G about Amy; the cavalry arrives, so they all take care of the bad guys.