The NCIS team investigates after a Navy petty officer, Kelsey Weaver, dies after overdosing on a dangerous new drug, flakka. With the help of one of Weaver's shipmates, they trace the flakka to a drug dealer with a local gang, the 1-1-3s, but he is killed before they can question him.
DNA evidence on the drug dealer's corpse leads them to a killer known as "The Ghost," who has been linked to the Triads, dangerous Chinese crime syndicates. The team suspects that the Triads have been using local gangs to sell the flakka locally.
Sebastian identifies The Ghost as Roger Liu, a Chinese businessman. Councilman Hamilton, now running for mayor, helps Pride get leverage on a 1-1-3 shotcaller named Kendrick. Kendrick leads Sonja to Liu. After Liu shoots Kendrick, Sonja is able to stall and then protect Kendrick until the rest of the team arrives and takes down Liu and his muscle.
The team realizes that Liu was being paid to flood the area with flakka by none other than Councilman Hamilton's opponent in the mayoral race.
Sebastian, meanwhile, discovers important clues in the altered pictures Brody has been receiving, leading them to a website that claims that the death of Brody's sister was no accident, but murder.