Decades after prophecy declared their rock music would unite the universe, aging slackers Bill S. Preston, Esq. and Ted "Theodore" Logan remain trapped in mid-life mediocrity, still married to princesses Joanna and Elizabeth. Despite endless efforts, they have failed to write the prophesied song. Their mundane reality shatters when a time-traveling emissary, Kelly, summons them to the future. The Great Leader informs them that reality is collapsing due to a tear in the space-time continuum, and they have exactly seventy-seven minutes to compose the unifying song, or all existence will be obliterated. Desperate and out of ideas, Bill and Ted hatch a plan to steal the song from their future selves by traveling forward in time. Meanwhile, their brilliant daughters, Thea and Billie, realize their fathers are doomed without help. Determined to save the universe themselves, the girls build their own
time machine and embark on a mission through history to assemble the ultimate backing band for their dads, recruiting musical legends like Jimi Hendrix, Louis Armstrong, Wolfgang Amadeus Mozart, Lingzi, and a cavewoman drummer named Groot. Back in the present, Bill and Ted bounce chaotically through the timestream, encountering increasingly bizarre, cynical, and elderly versions of themselves who refuse to help, culminating in a violent
confrontation with a murderous robot named Dennis Caleb McCoy, sent by the Great Leader’s misguided son to assassinate them. Bill, Ted, and the robot are killed, plunging them into the underworld, where they must navigate Hell and Heaven to reclaim their lives. They reconcile with Death, who has been estranged from the band since their last adventure, and convince him to join their cause. Reuniting with their daughters in the present, Bill and Ted realize a crucial truth: they cannot simply steal the song from the future because the song was never meant to be written by just the two of them. Instead, the magic requires everyone. As the sky tears apart and the fabric of reality disintegrates, Bill and Ted broadcast a massive global livestream, handing out musical instruments to every human being on Earth and throughout time. With their daughters conducting and the historical legends leading the rhythm, Bill, Ted, and billions of everyday people play the simple, unifying chord together. The resulting wave of harmonious joy repairs the space-time continuum, defeating the apocalypse and saving the universe in a triumphant celebration of friendship and rock and roll.