This is a shortened version of the 1945 Republic serial "The Purple Monster Strikes," which was released to television in 1966.

The latest assignment for respected detective Charlie Chan has come directly from the government and involves the disappearance of a scientist named Harper, who was working on an extremely important serum. When the scientist is killed, Chan must sort through all very likely suspects, including the man's sister and his butler.

Ore shipments are being stolen and the Rangers send Buck and his men to guard the next shipment. When that is stolen also, Buck is kicked out of the Rangers.

The Cattlemen's Association has called in the Mesquiteers to find cattle rustlers. They get Tex Riley to pose as Stony so Stony can arrive posing as a wanted outlaw. This gets Stony into the gang of rustlers and he alerts Tucson and Lullaby as to the next raid. But Hartley is on hand and unknown to anyone is the rustler's boss and he joins the posse with a plan that will do away with the Mesquiteers.

A rustler's son (Roy Rogers) courts a rancher's daughter (Mary Hart) during a range war.

A charming racketeer seduces the DA's stepdaughter for revenge, then falls in love.

A Martian invader crashes his spaceship conveniently close to the workshop of a scientist who is developing an interplanetary craft. If the extraterrestrial Purple Monster can complete the rocket ship and return to Mars, he will be able to start a full-scale invasion of Earth. Good thing Craig Foster sets out to thwart the Monster's mission!

An attorney handling a murder case is unaware his own wife played a crucial role in the killing.

Reporter Nicholas Ranson is jubilant when, on 17 Dec 1903, in Kitty Hawk, North Carolina, Orville and Wilbur Wright take their first airplane flight. Back home in Underwood, Maryland, however, his uncle Hiram F. Jenkins, owner and editor of the local newspaper, refuses to print the story. Nicholas quits and continues to work on his own airplane, with the devoted help of his little daughter Peggy. Peggy is actually the first in her family to fly when her friends, Patrick Falconer and Scott Barnes, induce her to get inside a large kite they have made, and run with it in a field until she is airborne. The kite is caught in a tree, however, and Peggy gets a black eye. Later, Nicholas dies when his experimental airplane crashes, leaving his wife and children alone. By Peggy's adulthood, planes are capable of flying at an altitude of 11,000 feet, and speeds of nearly 100 m.p.h. Peggy continues her father's obsession with flight by helping Scott and Pat to build a plane.

Brothers Beau, John and Digby Geste join the Foreign Legion, where they fall under the rule of tyrannical Sergeant Markoff. Beau and John are assigned to Fort Zinderneuf, where Markoff tries to break their spirit, aware of a dark family secret concerning a fabulous jewel one of them carries. As tensions rise, Arabs attack the fort and rivalries must be thrown aside in a desperate battle for life.