The supporting cast features Robert Young, Nicole Maurey and Thomas Mitchell, as well as a rare film appearance by Peruvian singer Yma Sumac.

American adventurer Harry Steele makes a living as a tour guide in Cusco, Peru but plans to earn his fortune by finding the legendary gold and jeweled "sunburst", a lost Inca treasure, at the ancient capital of Machu Picchu.

Bar owner Ed Morgan, who is older and feeling his age, has been searching for the treasure for fourteen years and hires a sniper to frighten off Harry.

With little money and the police on her trail, she plays on Harry's sympathy by informing him that she is fleeing from Anton Marcu, a Romanian official with a small plane who is pursuing her.

At Machu Picchu, they discover an archaeological expedition headed by Dr. Stanley Moorehead, who is preparing to enter the tomb where the sunburst is presumed to be located.

Harry falsely tells Moorehead that their plane needs gas and disables the expedition’s radio to block news of pursuit by the authorities.

Later, believing Morgan asleep, Harry slips away and enters the tomb, using a reflection of light on an artifact to highlight where the sunburst is hidden inside a hollow pillar.

In the meantime, in place of a ring, Harry gives Elena an ancient gold Incan pin that “fell into his pocket.” The film was originally known as Legend of the Incas.

A sixteen-person unit, including Heston, producer Mel Epstein and director Jerry Hopper, spent a month filming footage in Peru in 1953.

Throughout Secret of the Incas, the main character, Harry Steele, can be seen wearing what would later become known as the "Indiana Jones" outfit: brown leather jacket, fedora, tan pants, an over-the-shoulder bag, and revolver.

Raiders' costume designer Deborah Nadoolman Landis noted that the inspiration for Indiana's costume was Charlton Heston's Harry Steele in Secret of the Incas: "We did watch this film together as a crew several times, and I always thought it strange that the filmmakers did not credit it later as the inspiration for the series" and quipped that the film is "almost a shot for shot Raiders of the Lost Ark.