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 sergeant first-class retires from the Army, the day he becomes a civilian he is kidnapped. When his tortured body is found, the team must determine the reason behind the extreme cause of death.

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.