The Grissom Gang is a remake of the notorious 1949 British melodrama No Orchids For Miss Blandish. Kim Darby plays a 1920s-era debutante who is kidnapped and held for ransom. Her captors are the Grissoms, a family comprised of sadists and morons, and headed by Ma Barker clone Irene Dailey. One of the Grissoms, played by Scott Wilson, takes a liking to his prisoner, which results in a bloody breakdown of the family unit. Both The Grissom Gang and the original No Orchids For Miss Blandish were inspired by the best-seller by James Hadley Chase, though neither film retains Chase's original ending.
The story is set during the South American Wars of Independence. Simón Bolivar, the liberator, has escaped from Spanish custody with the aid of an idealistic Spanish officer, Captain Montserrat. The Spanish commander, Colonel Izquierdo ('left' in Spanish), threatens Montserrat with torture to find out where Bolivar can be recaptured.
In 1825, English peer Lord John Morgan is cast adrift in the American West. Captured by Sioux Indians, Morgan is at first targeted for quick extinction, but the tribesmen sense that he is worthy of survival. He eventually passes the many necessary tests that will permit him to become a member of the tribe.
Black militants building up an arsenal of weapons in preparation for a race war are betrayed by one of their own.