Round-Up Time in Texas

Gene Autry rounds up a large herd of horses in Texas and receives a telegram from his brother Tex, who is mining diamonds in South Africa. The message says Tex and his partner Barclay have made a big strike in the Valley of Suspicion and urges Gene to bring as many horses as possible to Dunbar, where he can contact John Cardigan, the saloon owner who grubstaked them. Gene and his sidekick Frog quickly decide to go overseas with the herd.

Gene and Frog quickly arrange passage overseas and accompany the horses to South Africa. They sail for the continent and head toward Dunbar once they land, ready to meet Tex's contact and pursue the mine. The journey sets the stage for international danger and diamond fever.

Tex and Barclay are ambushed by Cardigan's men on their way back to Dunbar. Barclay is killed and Tex is wounded but manages to escape into the jungle. Cardigan resolves to seize sole control of the mine and begins to tighten his grip on the operation.

Gene and Frog arrive at Dunbar and hire Barkey McCuskey, a small-time English con artist, as their auctioneer for selling the horses. The plan is to monetize the herd to fund their search and draw Tex and Barclay's attackers into the open. Dunbar becomes a hub of scheming and sales.

Cardigan tells Gene that Tex is being hunted for Barclay's murder, prompting Gene to defend his brother. Gene grows suspicious when he notices Cardigan tampering with a telegram from Tex, suggesting he cannot be trusted. The tension between loyalty and deception grows as the plot thickens.

Gene spots Cardigan's servant Namba wearing the belt buckle that Gene had given Tex, deepening his distrust of Cardigan. Johnson, Cardigan's henchman, plans to kill the Texans that night and passes uncut diamonds to Frog in exchange for a horse, highlighting the illegal diamond trade. The auction becomes a front for criminal schemes.

After the arrest of Gene and Frog, the South African police take them to Kimberly for trial, but the Texans manage to escape before conviction. The escape deepens their resolve to uncover Cardigan's plans and find the mine. They press on despite the legal danger surrounding them.

The group is captured by natives and brought before Chief Bosuto. Frog wins the chief over by teaching his children to sing, earning a temporary reprieve for the others. The chief agrees to release everyone except Frog, who stays behind to teach more music, while Gene, Barkey, and Gwen are led away by Namba.

Police arrive and free Cardigan, and Gene, Barkey, and Gwen are then directed toward Cardigan's jungle hideout where Tex is being held as a slave. Gene and his companions pursue the plan to rescue Tex and the other workers. The dangerous trek leads them into Cardigan's stronghold.

Gene arrives and frees his brother and the other workers. Cardigan and Johnson attempt to escape with Gwen as a hostage, but Frog catches Johnson and Gene fights Cardigan, who falls from a cliff to his death. The police arrive and capture the rest of Cardigan's gang, ending the threat.

On the ship returning to Texas, Frog sings along with Bosuto's children as the journey home continues. Gene and Gwen share a kiss, signaling a hopeful ending after the perilous mission and the defeat of Cardigan.