Two Americans, Bud Abbott and Lou Costello, find themselves stranded in Cairo, where a chance overheard conversation sets their adventure in motion. They listen as Dr. Gustav Zoomer explains the legend of Klaris, the ancient mummy who guards the Tomb of Princess Ara, and a sacred medallion said to pinpoint the treasure’s exact location. The tale becomes even more tangled when Klaris’s followers, led by Semu, cross paths with the scheming Madame Rontru, a businesswoman determined to lay her hands on the wealth.
Eager for a way out, Abbott and Costello head to the doctor’s house to apply for a job accompanying the mummy back to America. Fate, however, intervenes in the form of a violent interruption: two of Semu’s men, Iben and Hetsut, murder the doctor and steal the mummy just before the pair arrive. The medallion is left behind, and the two comic travelers soon pick it up, fantasizing about selling it. Rontru offers a quick $100, but Abbott suspects its true value runs far higher and presses for a heftier sum—$5,000—which Rontru agrees to pay.
Rontru then sets up a meeting at the Cairo Café, where a waiter warns them that the medallion is cursed. In a frantic scramble, the artifact shuttles between hands until it bizarrely winds up in Costello’s hamburger, and he ends up eating it. To get a clearer read on the medallion, Rontru drags the pair to a doctor’s office for a fluoroscope exam, but the inscriptions prove unreadable because they’re carved in hieroglyphics that resist modern interpretation.
Semu reappears, this time posing as an archaeologist who offers to guide them to the tomb. Meanwhile, Semu’s followers have revived Klaris, turning the mission into a far darker pursuit. The group reaches the tomb, and Costello learns of Semu’s murderous plan to eliminate them all. Rontru captures Semu, while Charlie, one of her men, disguises himself as a mummy and slips into the temple. Abbott follows suit, also donning a mummy disguise, and the two rescue Semu from danger.
The temple scene crescendos as all three mummies converge in one place. A plan involving dynamite to reach the treasure goes awry, detonating and destroying Klaris while exposing the treasure itself. In the unexpected aftermath, Abbott and Costello convince Semu to pivot the temple’s fate away from greed and toward preserving Klaris’s legend by turning the place into a nightclub, ensuring the story of Klaris endures in a more playful, enduring form.
