Britt Reid is enjoying a vacation in Hawaii, but during his absence, racketeers install one of their men on Reid's newspaper as Managing Editor. A gunman is also sent by the criminals to Honolulu to prevent Reid's safe return home.
Britt Reid receives a lead that prompts him to investigate the Kolten Munitions Plant. After a visit to the plant proves unsatisfactory, Reid calls on the Plant's Superintendent at his home and learns of a crime syndicate's devious plan.
Britt Reid learns that Frances Grayson, heiress of the Aluminum Product's fortune, is being victimized by racketeers. Disguised as The Green Hornet, he visits the Grayson home only to find an actress impersonating Miss Grayson.
Determined to seize control of Aluminum Products Company, racketeers plan to cripple Home Electric, the company supplying the Aluminum Products Company with the power they need to stay in the business. It is time for The Green Hornet.
Crogan, leader of the racketeers, sends Deluca with a crew to run rifles over the border. When Axford and Lowry become involved in an accident with the truck transporting the rifles, they identify Deluca and follow him back to the city.
Britt Reid sends two of his reporters to search the wreckage of a bombed warehouse where they discover evidence linking the warehouse to Grimbolt Steel Mills where frequent suspicious accidents have been occurring.
While continuing his investigation into Grimbolt Steel Mills, Britt Reid learns that Dr. Bedloe worked with Weaver on the anti-aircraft bomb responsible for many accidents. As The Green Hornet, Reid visits Dr. Bedloe.
Desperately in need of some quick cash, Crogan is inspired by an idea he gleaned from an article in The Sentinel. Concerned about the matter, Britt Reid sends Axford to guard Frances Grayson, the victim mentioned in the article.
Infuriated by an article in The Sentinel exposing his band of racketeers, Crogan turns up the heat on Reid's newspaper. Soon, hoodlums attack a Sentinel delivery truck, but leave behind a crucial piece of evidence.
Britt Reid and his staff rejoice over a report that an oil well they helped John Fulton finance will prove lucrative. However, Fulton soon bursts into Reid's office to report that a lawyer who holds his $10,000 bank note is up to no good.
Upon witnessing the hijacking of a truckload of silk, Reid and Axford follow the hijackers, but are soon ambushed, at which point Axford is taken prisoner. It is time for The Green Hornet.
A considerable amount of auto thefts prompts Britt Reid to take Miss Case and Axford to investigate a roadhouse that is notorious for racketeering activity. Their presence does not go unnoticed and matters quickly turn dangerous.
Britt Reid suspects a conspiracy to defraud insurance companies is afoot when a third warehouse reported to contain military supplies is destroyed by a fire. As The Green Hornet, Reid decides to question the owner of the warehouses.
Britt Reid learns that Foranti, the head of the Builder's Association, is stealing Association funds. As The Green Hornet, Reid confronts Foranti, but when Breedon, Foranti's undercover agent, is called, things take a turn for the worse.
After The Green Hornet narrowly escapes with his life, clues pointing to the syndicate's top brass arrive at Reid's desk via messenger prompting him to set up an interview with Crogan. The syndicate decides it is time to change things up.
