In the year 2691, the utopian society of the future is built upon the music of Bill S. Preston, Esq. and Ted "Theodore" Logan, members of the rock band Wyld Stallyns. However, the peace is threatened by Chuck De Nomolos, a villain who despises this harmonious world. He devises a plot to send robot doubles of Bill and Ted back to present-day San Dimas, California, to kill them and destroy their promising music careers before their influence can take root. Unaware of the danger looming over them, the real Bill and Ted prepare for the San Dimas Battle of the Bands with hopes of winning and securing their destinies as musical saviors.

As part of De Nomolos' plan, the evil robot versions of Bill and Ted succeed in their mission, leading the real Bill and Ted into a perilous journey through the afterlife. They encounter Death, engage in surreal trials and experiences, and eventually find allies in their quest to return to the world of the living. Determined to stop De Nomolos, the duo faces numerous challenges while relying on their eternal friendship and love for music. Along the way, they learn crucial lessons about trust, perseverance, and destiny without realizing that their greatest adventure has only just begun.