Bill and Ted, now middle-aged fathers, are still struggling to create the world-changing song they were destined to write. As their lives begin to unravel and their marriages face strain, they receive a visit from the future. Kelly, the daughter of their old mentor Rufus, warns them that time and reality itself are collapsing, and only their music can save the universe. Given a tight deadline, the duo decides to travel through time and steal the song from their future selves.

Meanwhile, their daughters, Thea and Billie, embark on their own journey through time to assemble a legendary band to aid their fathers in creating the ultimate song. As both generations of Wyld Stallyns navigate various historical periods and encounter famous musicians, they face numerous comedic obstacles. Bill and Ted ultimately must confront their own insecurities and failures as they race against an imminent cosmic disaster.