In the early 1920s, an archaeological expedition led by Sir Joseph Whemple discovers the mummified remains of the ancient Egyptian priest Imhotep, buried alive for sacrilege. Alongside the mummy, they unearth the Scroll of Thoth, a fabled artifact said to have the power to bring the dead back to life. Despite the warnings from Dr. Muller, an occult expert, Sir Whemple’s assistant, Ralph Norton, reads the scroll aloud, inadvertently resurrecting Imhotep. The shock drives Norton to madness as Imhotep, now revived, escapes and vanishes into the depths of Cairo.

Years later, Sir Joseph’s son Frank and Dr. Muller collaborate on another excavation, where they encounter a mysterious man named Ardath Bey. Bey assists them in discovering the tomb of Princess Anck-su-namun, who had been Imhotep's lover. Unbeknownst to the archaeologists, Ardath Bey is actually the revived Imhotep seeking to use the Scroll of Thoth to resurrect Anck-su-namun. As the archaeologists work, Imhotep begins to manipulate Helen Grosvenor, a woman who bears a striking resemblance to Anck-su-namun, drawing her into his dark plans. Thus begins a battle between the modern world’s skepticism and the ancient powers of a relentless, resurrected priest.