The stakes are higher than ever for the time-traveling exploits of William "Bill" S. Preston, Esq. (Alex Winter) and Theodore "Ted" Logan (Keanu Reeves). Yet to fulfill their rock and roll destiny, the now middle-aged best friends set out on a new adventure when a visitor from the future warns them that only their song can save life as we know it. Along the way, they will be helped by their daughters, a new batch of historical figures, and a few music legends — to seek the song that will set their world right and bring harmony in the universe.