The relatives of a recently deceased man gather at his eerie mansion but before his will can be read, they start being murdered one by one.
Two American gun runners at odds with each other and looking to sell guns to the rebels during the Cuban War of Independence navigate a boat to Cuba. Along for the ride is a beautiful Cuban rebel in who both men are interested.
A young doctor taking a break from work is shot in the head, and the police can't find a clue even as to a possible motive. Inspector Al Gordon (John Alexander) decides that he has to put some men on duty at the hospital, and one of them is Fred Rowan (Richard Conte), a detective with experience as an army medic, masquerading as an intern. What Rowan finds is a high-pressure world in which interns are hopelessly squeezed for time, sleep, energy, and -- most of all -- money, and walk a fine line on the edge of personal and professional disaster.
Rodeo champ Gene Autry inherits half interest in both a ranch and a mine that provides steady employment for the surrounding rancheros. Unfortunately, the other half goes to Easterner Barbara Erwin (Carol Hughes), who is only interested in monetary remuneration. To convince Gene to buy her share, Barbara enters into an unholy alliance with unscrupulous attorneys Arnold (Ivan Miller) and Fry (Sam Flint), who, without their client's consent, hire a gang of thugs headed by Tommick (John Merton). When a ranchero (Elias Gamboa) is mortally wounded in the ensuing gun battle, Barbara sees the error of her way and switches sides.
A mad scientist named Dr. Satan plots to steal key pieces of technology to enable him to build an army of robots based on his prototype to conquer America. The only one standing in his way is Bob Wayne, who fights Satan as the enigmatic Copperhead. Mysterious Doctor Satan is a 1940 film serial named after its chief villain. Doctor Satan's main opponent is the masked mystery man, "The Copperhead", whose secret identity is Bob Wayne, a man searching for justice and revenge on Satan for the death of his step-father. The serial charts the conflict between the two as Bob Wayne pursues Doctor Satan, while the latter completes his plans for world domination.
The nefarious Dr. Fu Manchu searches for the keys to the tomb of Genghis Khan, in order to fulfill a prophecy that will enable him to conquer the world. His nemesi, Dr. Nayland Smith and his associates fight to keep the evil doctor from getting his hands on the keys. In 1943 the serial was edited together into a feature movie also called Drums of Fu Manchu.
The mysterious Don Del Oro ("Lord of Gold"), an idol of the Yaqui Indians, plans to take over the gold and become Emperor. Francisco was put in charge of a legion to combat the Yaqui tribe and protect the land, but when attacked Zorro came to his rescue. Francisco's partner recognized Zorro as the hidalgo Don Diego Vega, then ask him to take over the fighting legion as his alter-ego Zorro.