Bill et Ted sont des cancres au collège. Mais avec l'aide de Rufus, ils ont mis au point une machine à voyager dans le temps sous la forme d'une cabine téléphonique. Ils naviguent ainsi dans l'histoire et le futur à la rencontre d'embûches et aventures diverses. Mais toujours ils arrivent à survivre grâce leur talent d'explorateurs.
In the small town of San Dimas, a few miles away from Los Angeles, there are two nearly brain dead teenage boys going by the names of Bill S, Preston ESQ. and Ted Theodore Logan, they have a dream together of starting their own rock and roll band called the "Wyld Stallyns". Unfortunately, they are still in high school and on the verge of failing out of their school as well, and if they do not pass their upcoming history report, they will be separated as a result of Ted's father sending him to military school. But, what Bill and Ted do not know is that they must stay together to save the future. So, a man from the future named Rufus came to help them pass their report. So, both Bill and Ted decided to gather up historical figures which they need for their report. They are hoping that this will help them pass their report so they can stay together.