The Mummy (1999) plot, in full, is a chain of cause and effect that starts with one book being read aloud. The film opens in ancient Egypt, where the high priest Imhotep and the pharaoh's mistress Anck-su-namun kill the pharaoh. She takes her own life, and Imhotep is mummified alive and sealed away under a curse. That curse is the legend the film asks you to accept, and it exists only inside the story.
In 1926, Evelyn Carnahan and her brother Jonathan find a puzzle box that points to the lost city of Hamunaptra. They persuade Rick O'Connell, who once saw the city, to take them there. A team of American treasure hunters led by Beni Gabor competes with them at the site, so the dig becomes a race as much as a search.
Evelyn finds a golden book and, against Rick's advice, reads aloud from it. That wakes Imhotep. The mummy begins to regenerate by draining life from the people he kills, and he brings the plagues of Egypt down on the land. It is a neat rule for a creature: he needs victims to rebuild his body, so every scene of him gaining strength costs someone their life.
He captures Evelyn, because he needs her as a sacrifice to bring Anck-su-namun back to life. Rick, Jonathan and the Medjai warrior Ardeth Bay, who has spent his life guarding against this return, race back to Hamunaptra to stop him. They fight through Imhotep's servants and rescue Evelyn at the last moment. Evelyn uses the other book to take away his immortality, and Rick drives a blade into him. Imhotep sinks back to the underworld and the city starts to collapse. The heroes escape with some treasure while Beni meets a grisly end in the ruins.