NCIS: Los Angeles - Season 4 (2012)

A man dies in a deliberate hit-and-run incident; the victim was a staffer of a candidate for the US Senate; G and company investigate; Kensi goes undercover as the replacement for the vic; the team solve the puzzle and nail the bad person.

Sam answers a call for help from a former fellow worker at the CIA; Sam finds him dead of hanging; he gets an encoded message, which, when decrypted, is a list of names; the team realize the implications; Hetty calls the FBI. [Continued.]

After the decryption of a list of names, NCIS agents continue the search for both Sidorov, a Russian illegal-arms dealer, and leftover Russian sleeper agents with access to surreptitious nuclear bombs; NCIS teams execute concurrent arrests in seven cities around the USA; however, all seven teams find their targets already dead. G and Sam confer with Arkady; afterward G and Sam meet a tail, which consists of three CIA agents, one of whom, Snyder, Sam knows and dislikes; Kensi, Deeks, and others uncover an empty but radioactive secret room; Eric and Nell find Sidorov; ...

A man stops an ambulance, kills the EMTs, stabs the patient, and removes an object from his chest; the victim was a civilian scientist working for the US Navy; G and Callen put the puzzle together and find both the killer and the object.

A retired CIA agent dies when a lighter explodes; G and company investigate because Hetty requests the case; the fearless foursome check out high-priced call girls and more, and they defy orders, but they find the truth and the bad person.

Deeks is away to testify in court, so Granger teams with Kensi. A gang stop an armored truck, attack the crew, and steal the cargo, consisting of 100 gold bars, valued at $70M, en route to the People's Bank of China; footage abounds; Callen and company investigate. G and Sam find a dead clown, and Nell IDs him; G, Sam, and Kensi find three executed thieves; Kensi talks with the girlfriend of the sole surviving thief (Welch), then she, G, and Sam find Welch's body, and Kensi finds the gold; G and Sam check the gold, which is not gold. Hetty comments to G in private ...

An NCIS agent dies aboard an aircraft carrier at sea; the fearless four, undercover, fly to the ship, where they meet even more problems, but they eventually solve the crimes; Hetty joins them for Christmas underway; Nell catches Eric.

At 03:06 Deeks receives a call from a woman, Jenny, in two of his past lives; she tells about a ring stealing luxury SUVs and shipping them to the Far East; Jenny disappears; the team solve the puzzle, grab the bad guys, and rescue Jenny.

Two weeks ago a Marine lieutenant, Edwin, died in Afghanistan; the local civilian coroner has done an autopsy by the request of the widow, Antonia; she also has hired a private investigator, Stuart, to look into the circumstances; last night someone killed Stuart by slitting his throat; Callen and company investigate. G and Sam meet Antonia, who describes her suspicions about a cover-up; Rose, a medical examiner, explains about the harvesting of tissue, but Antonia objects, saying that Edwin was not an organ donor; Edwin's file has disappeared from the coroner's ...

A passenger in a van shoots an LAPD cop, who shoots the driver, then the passenger speeds away; the driver was a Chechen-American with ties to a terrorist network; G goes undercover and into trouble; the team solve the case and rescue G.

In Mexico a US joint team makes a raid to capture the head of a drug cartel; due to a leak the team walks into an ambush; Granger tasks the gang to pinpoint the breach; they go undercover, find the leak, grab the head man, and rescue Nell.

Dean, a fugitive terrorist who disappeared in 1973, stumbles in from a woods, collapses, and dies of a stab wound; G and company investigate; the team find the pieces and fit them together; they find also explosives and one more bad guy.

A thief steals a used notebook computer from a store; a car hits the thief, and two occupants of the car stuff the victim into the back seat; the thief is Amir, the nephew of Yusef, whom Sam still owes on a debt incurred in Afghanistan some years ago; a third occupant of the car, Habib, is a known terrorist; Callen and company investigate (after several tense moments at the start). While Sam visits Yusef, bad guys drive by and open fire; Sam returns fire and drops one of them, Ali, a member of a radical jihadist group; Eric learns that Ali and Amir knew each other; ...

One Russian kills another in the LA area; G and Sam quiz Arkady; Sam and Michelle go back undercover for the CIA; Sam lands in jail, and Hetty leaves him there; Greshnev dies, and Sidorov disappears; Hetty says that this is far from over.

In Idaho someone executes a Marine gunnery sergeant with a pistol; two days before in Los Angeles someone used the same weapon in the same way to kill an Indonesian man; the LA bunch collaborate with an NCIS mobile team. [Continued.]

The G gang and the Red Team continue to pursue Spears and other bad guys; attention turns to a big player in illegal immigration and a man with a red scarf; Hetty sees that Spears is not the executioner, then the teams catch the right one.

A Naval aviator dies of cyanide poisoning, as does a dancer, at a bikini bar near Los Angeles; another officer survives and gives a clue; the team find the cyanide, the hardware, the motive, and the bad guys, and they prevent a tragedy.

Nell reports the death of the kingpin of a Mexican drug cartel in a police shootout; the body of the victim disappears from the morgue as soon as it arrives; G and company investigate the possibility of a leak, and they discover the truth.

Gunmen stalk and attack a woman, who disappears; three others die; Hetty cryptically assigns G and company to investigate; Hetty finds the woman, an NCIS agent undercover; the team catch the bad guys; G and Hetty discuss backgrounds.

Monica becomes the target of an unknown shooter in Hollywood; Deeks, in an undercover role as Max (at the direction of Granger), rescues her; Monica is a hostess at a nightclub, which is a property of a South African who's now a legitimate businessman, but who previously worked as an international dealer in illegal arms. G and Sam visit the club, and Nell identifies the shooter as Pieter, an enforcer from South Africa; G and Sam take a different tack with Pieter, so they meet him and take him to the boathouse; Max has an unusual short-term relationship with Monica, ...

A nuclear bomb explodes in a desert in Mexico; G and company investigate; Sam and Michelle go underground; G and Kensi go to Iran and bring back the Chameleon, who takes part in a complex deal to gain the two missing bombs. [Continued.]