Andoheb (George Zucco), the High Priest of Arkam, summons Yousef Bey (John Carradine) to the temple to pass on the high priesthood to his successor. In Mapleton, Massachustts. Professor Matthew Norman (Frank Reicher) explains the legends of Arkam and Karis (Lon Chaney) to his history class, who scoff. But after the class, one of the students, Tom Hervey (Robert Lowery) meets up with his girlfriend Amina Mansori (Ramsay Ames), a beautiful Egyptian woman. Strangely, she becomes dreamy whenever Egypt is mentioned.
Back in Egypt, Andoheb informs Yousef Bey that the mummy Kharis still lives and he must bring him and the body of Ananka back home. He must brew nine tana leaves and Kharis will find him. As Kharis passes Amina’s home, she follows him in a trance. Kharis arrives at Professor Norman’s home and strangles him and drinks the fluid. Amina sees Kharis and faints, and a birthmark appears on her wrist. The Sheriff (Harry Shannon) and the coroner (Emmet Vogan) find a strange mold on the Professor’s throat and know that it means the mummy is back again. Yousef Bey calls on Amon-Ra for help and begins to summon Kharis. The mummy comes, killing a farmer on the way, and the sheriff organizes a search.
The next day, at the Scripps Museum, Yousef Bey emerges as Kharis breaks into the museum. Kharis tries to touch the mummy of Ananka, but it disintegrates. This means that she has been reincarnated in another body. Kharis tries to destroy the museum, killing a security guard in the process, and Inspector Walgreen (Barton MacLane) and Doctor Ayad (Lester Sharp) try to trap Kharis in a pit. Amina decides to elope with Tom to New York, but Yousef Bey sends Kharis to seek her out.
Inspector Walgreen sets the trap for Kharis. Amina is awakened as Karis approaches and, hypnotized, walks into the yard. Kharis recognizes her as the reincarnation of Ananka. She faints as she is carried away. A group of townspeople pursue. Kharis arrives at the mill and presents Amina to Bey, who falls for her beauty and desires to keep her alive. Kharis is enraged and kills Bey. Tom races to stop Kharis. The mob pursues Kharis into a swamp and he and Amina sink together into the water. The story will be continued in The Mummy’s Curse.
The film was directed by Reginald Le Borg from a script by Griffin Jay, Henry Sucher, and Brenda Weisberg. Some reviewers thought it the best of the Mummy pictures, but others considered it unimpressive. Lon Chaney was injured smashing real glass on the set. He injured Frank Reicher by choking him too forcefully. The actress who was to play Ananka hit her head and passed out with a concussion, and she was replaced by Ramsay Ames. Very few Universal horror classics killed off the female lead. This was one, but she came back in the sequel.