Postal inspectors Frank Marshall and Slim Hewitt infiltrate a Ku Klux Klan-like vigilante group which has mailed a bomb to a senator. When the legion kills Nancy Foster's brother, she helps Frank and Slim in their investigation.

Two newly-appointed postal inspectors, Frank Marshall and 'Slim" Hewitt, set out to track down the sender of a time-bomb to a U.S. Senator; during their investigation, they run across a hooded organization that is terrorizing an American city. They also meet Don Foster, who is loud in his condemnation of the terrorists, and his sister Nancy, who fears for her brother's life.—Les Adams <[email protected]>