It's the 22nd century. Earth has passed through two apocalypses (one occurring in the predecessor, Kamandi: At Earth's End). A group of emotionless, logical cyborgs named the Biomech Sevens are overseeing Earth's return to greatness. For the last year, Superman has been regaining his lost strength in a hovering city, where he is able to receive the benefits of the sun's rays. While recuperating, he learns that Gotham City is next in line to be "cleansed", via a nuclear bomb. It has been overrun with mutants and other such degenerates.