In 3067 BC, the Scorpion King leads his army on a campaign to conquer the world. After fighting for seven years, his army is defeated while attacking Thebes and exiled to the desert of Ahm Shere; his men die of heat exhaustion. After vowing to give Anubis his soul for the power to defeat his enemies, an oasis forms to hide the Scorpion King's pyramid and he is given a legion of jackal warriors in Anubis' image. The Army of Anubis sweeps across Egypt, but once their task is finished, Anubis claims the Scorpion King's soul and his army.
In Thebes, Egypt, 1290 BC, high priest Imhotep engages in an affair with Anck-su-Namun, the mistress of Pharaoh Seti I. When the Pharaoh discovers their tryst, Imhotep and Anck-su-Namun kill him. As Seti's guards arrive, Imhotep flees while Anck-su-Namun kills herself, intending for Imhotep to resurrect her. After Anck-su-Namun's burial, Imhotep and his priests steal her corpse and travel to Hamunaptra, the city of the dead, where they begin the resurrection ceremony. However, the group is intercepted by Seti's bodyguards, the Medjai, before the ritual could be completed, and Anck-su-Namun's soul is sent back to the Underworld. Imhotep's priests are all mummified alive. Imhotep himself is sentenced to immortal agony, condemned to suffer the Hom Dai curse: having his tongue removed and then being buried alive with flesh eating scarab beetles. Imhotep is buried under high security, sealed away in a sarcophagus at the feet of a statue of the Egyptian god Anubis, and kept under strict surveillance by the Medjai, since if Imhotep were ever to resurrect, the entire world would be doomed.
A massive metal ring with engraved cover stones is discovered in the sands of Giza, Egypt in 1928, by an archaeologist named Langford and his young daughter, Catherine. Many years later, the elderly Catherine Langford offers Egyptologist and linguist Daniel Jackson the chance to translate the Egyptian hieroglyphs on the cover stones. Jackson accepts and travels to a US Air Force installation where he examines the stones. Special Operations Colonel Jack O'Neil arrives to take command of the project and he declares it "classified" before Jackson can begin his research.
The film takes place in New York City in the year 2095 where genetically altered humans live side by side with unaltered men and women, and where Central Park has been mysteriously encased in an "intrusion zone" where people who attempt to enter are instantly killed. A strange pyramid has appeared over the city; inside, the gods of ancient Egypt have judged Horus, one of their fellow gods, to cease his immortality.
An ancient Egyptian priest called Imhotep (Boris Karloff) is revived when an archaeological expedition in 1921, led by Sir Joseph Whemple (Arthur Byron), finds Imhotep's mummy. Imhotep had been mummified alive for attempting to resurrect his forbidden lover, the princess Ankh-es-en-amon. Whemple's friend, Dr. Muller (Edward Van Sloan) inspects the mummy and exclaims "The viscera were not removed. The usual scar made by the embalmers knife is not there." Sir Joseph Wimple responds, "I guessed as much." Despite Muller's warning, Sir Joseph's assistant Ralph Norton (Bramwell Fletcher) reads aloud an ancient life-giving scroll – the Scroll of Thoth. Imhotep escapes from the archaeologists, taking the Scroll of Thoth, and prowls Cairo seeking the modern reincarnation of Ankh-es-en-amon.
In Ancient Egypt, during the monotheistic regime of Akhenaten, Akhesa is a beautiful princess, 14 years of age. An impetuous young girl, Akhesa rebels against her father's dictats. She refuses to live confined in the royal palace and wants to discover why her mother, Queen Nefertiti, has been exiled on the island of Elephantine. Assisted by her half-brother prince Tutankhaten, or "Tut", Akhesa flees the court in hopes of finding her mother. In defiance of danger the two teenagers travel down the Nile to the burning-hot desert dunes, courageously facing the mercenary Zannanza and priests of Amun Ra, who are conspiring to overthrow the pharaoh because of his rejection of their god. With innocence their only weapon, Akhesa and Tut overcome many hardships, and encounter an extraordinary destiny.