In a beach town on the Black Sea in Romania, G, Sam, Kensi, and Deeks check out the neighborhood while Hetty chats with the head of the Comescu family, who describes a connection to G. The team shoot their way into a house and save Hetty.

In Beverly Hills two masked thugs kidnap a wealthy and successful software developer; Callen and company help the National Security Agency; the team find the pieces and put them together, then they find the missing guy and the bad ones.

A Marine staff sergeant dies in an explosion of an SUV; Callen and company investigate; Hunter makes changes; Sam and Deeks find a runner and a bomb; the team find the bad guy; three more bombs explode, but the gang escape; Hetty returns.

While raiding a pawnshop, targeting a Mexican drug cartel, LAPD cops kill two cartel grunts plus a wanted Muslim terrorist; the LAPD requests help from Callen and company, who seek, find, and scrub an alliance between the two rogue groups.

A woman former lieutenant commander in Naval intelligence dies by gunfire; Callen and company find confusing and conflicting clues, but they put all the pieces together; Hetty again visits an old friend but says that she arrived too late.

A separated Marine attacks and beats a Japanese man tourist, who dies later; Callen and company investigate; the Marine tells a long story, which eventually becomes confirmed; the team, using extreme tact and discretion, achieve their goal.

The team are sent to the Mexican desert when a Naval Seaman is murdered over a mysterious box.

The CIA loses contact with Sam in Sudan with a CIA task force; two CIA agents die, as does a third one; G goes to Khartoum and lends a hand; the gang in LA help, and they find and deal with a mole; G and Sam return to LA and take a friend.

During a sting Deeks appears to blow away an unarmed bad guy; Hetty fires Deeks after the LAPD cuts its ties with the NCIS; Kensi belatedly learns about a ruse; the team and the LAPD together find a mole, the bad guys, and some explosives.

At a college a man steals an experimental electromagnetic-pulse weapon, which has the capability to render disastrous damage; Callen and company investigate the theft and a second one, and they figure out the case and provide a resolution.

G decks a man, who is the new assistant director, and who briefs the next case. A man dies of a gunshot, said to be self-inflicted, by his wife's firearm; both have worked for a think tank under contract to the DoD; the team solve the case.

Two men die in LA; a visitor, introduced as an Interpol agent, seeks help with a link to a closed NCIS case; Callen and company pursue a chameleon, who promises to kill G soon and tells why; Granger says he's there to catch a killer.

Granger summons Kensi to the boathouse; Hetty summons the others to the ops center; Kensi's father's fellow Marines have started dying, and Granger wonders whether Kensi is involved; the team start investigating and producing. [Continued.]

In LA a man survives gunfire while trying to enter the Vietnamese consulate; G and company investigate; the victim's personal effects include the name of a Marine first lieutenant; the team save lives, solve the case, and reunite a family.

A group of Marines find the dismembered body of a Navy ensign; Callen and company investigate; circumstantial evidence points to a SEAL, but Sam refuses to believe; Sam, a SEAL, hears the whole story; Callen learns the cause of death.

A bomb explodes in the bed of the pickup truck of a Marine former second lieutenant; he runs; FBI agents bust him; Granger wants to find out why the team did not previously know about a terrorist plot in the LA area; they figure it out.

G and Sam return from an investigation in Honolulu; Danny and Chin, of Hawaii Five-0, accompany them; they seek to intercept a rogue epidemiologist with smallpox virus; the team figure out the case and prevent an unimaginable disaster.

A driver causes a wreck and shoots to death the second driver; a third one blows away the first; SA Renko of the NCIS is an undercover worker of the gun shop where the first two men worked; the team find the bad guy behind it. [Continued.]

The Chameleon says that he'll walk; he tells about Renko and the Mayfield family; he demands an exchange of himself for an abducted NSA analyst; Granger cuts him loose, and the team escort him to the swap, but G takes action. [Continued.]