New York, early 1960s. Against the backdrop of a vibrant music scene and tumultuous cultural upheaval, an enigmatic 19-year-old from Minnesota arrives in the West Village with his guitar and revolutionary talent, destined to change the course of American music.

While working underground to fix a water main, Brooklyn plumbers—and brothers—Mario and Luigi are transported down a mysterious pipe and wander into a magical new world. But when the brothers are separated, Mario embarks on an epic quest to find Luigi.