In 1921, the Held expedition to Egypt, which is led by Sir Joseph Whemple, has discovered the mummy of Imhotep. A high priest, Imhotep was buried alive in the Temple at Karnak. Doctor Muller, who believes in the occult, warns the rest of the expedition of the curse that is imprinted on the gold seals of the Pharoah Amenophis. Knowledge of the curse proves too much of a temptation for Whemple's Oxford assistant, who examines the Scroll of Thoth and goes insane as he sees Imhotep's mummy come to life and take the scroll. Eleven years later, Frank Whemple, Sir Joseph's son, together with Professor Pearson, leads another archaeological expedition. An ageless Egyptian, Ardeth Bey, shows them where to dig for the unplundered tomb of Ankh-es-en-amon, who was a daughter of royalty buried 3,700 years earlier. The tomb is a sensational find, and Ankh-es-en-amon's coffin is placed in the Cairo museum. At the same time, Helen Grosvenor, whose mother was Egyptian, is attracted to her ancestral homeland and is summoned telepathically to the museum as Bey tries to revive the body of Ankh-es-en-amon by reading the Scroll of Thoth. The Whemples find Helen unconscious at the museum door and take her home to recover, while a museum guard dies of shock upon discovering Bey, who then accidentally leaves the Scroll behind in the museum. Frank tells Helen that he fell in love with the beautiful Ankh-es-en-amon during the excavation, and that Helen resembles her. When Bey enters the Whemple home to see Helen, Muller, Helen's doctor, who believes Bey to be the revived mummy, confronts him with the Scroll and a photograph of the mummy of Imhotep. With his eyes glowing hypnotically, Bey causes Sir Joseph to suffer a heart attack when he tries to burn the Scroll and compels the Whemple's Nubian servant to steal it. Under Bey's spell, Helen goes to his temple, where he reveals to her their past: In ancient Egypt, after Ankh-es-en-amon died, Imhotep, who loved her, stole the forbidden Scroll and dared the gods by trying to bring her body back from the dead. Discovered performing this unholy deed, Imhotep was sentenced to be buried alive in an unmarked tomb, along with the Scroll. After returning to Frank, Helen, half-conscious, asks him to save her. Again summoned by Bey's incantations, Helen escapes from her nurse, Frau Muller. In the Cairo museum, Bey dresses Helen in robes and jewels belonging to Ankh-es-en-amon. Bey, who still loves her as he did centuries earlier, tells Helen she must be killed and mummified before he can raise her from the dead to become, like him, a living mummy. Bey burns the actual mummy of Ankh-es-en-amon, as he believes her soul has been reincarnated in Helen. Frank and Muller are powerless before Bey's spells, so Helen entreats the god Isis for assistance. The god's statue raises its arm to point a glowing ankh at Bey, who ages and crumbles to dust. Frank then calls Helen back to the world of the living as the Scroll of Thoth burns.