Experimenting in hypnotic regression to past lives, Dr. Almada discovers that his fiancée, Flor, is the reincarnation of an Aztec maiden who was put to death for loving an Aztec warrior, her body placed at the entrance to a hidden chamber in the Great Pyramid of Yucatan where the treasures of the Aztecs were hidden, and her lover mummified but cursed to remain alive and guard the treasure. With her recovered memories, Flor is able to lead Almada, his wimpish assistant Pincate, and her father to the now-skeletal remains of the maiden. Attached to them is a golden breastplate with a map detailing the route to the treasure. But to their horror, the party is intercepted by the mummified warrior, Popoca, and flee with the breastplate back to Mexico city. Popoca follows. In the meantime, Prof. Krup, an unscrupulous colleague of Almada's, recruits a gang of thugs, whom he leads from behind a mask and known only as "The Bat". Both Krup and his gang, and the mummy, converge on Flor's house to retrieve the sacred breastplate, which is in her possession...