Maciste arranges for himself and his new friend Bangor to be captured by a mysterious band of white-clad marauders and taken to an underground city. There the two are forced to turn an enormous wheel along with other captives as part of a gold-and-diamonds mining operation. The underground city's queen, Halis Mosab, takes note of the handsome, muscular Maciste and chooses him to be her consort if he can meet such challenges as saving the kidnapped Princess Saliura from a gigantic ape. Maciste ki...