When 9 first comes to life, he finds himself in a post-apocalyptic world. All humans are gone, and it is only by chance that he discovers a small community of others like him taking refuge from fearsome machines that roam the earth intent on their extinction. Despite being the neophyte of the group, 9 convinces the others that hiding will do them no good.

The musical tells the story of Elisabeth ("Sissi"), the Empress of Austria, from her engagement and marriage in 1854 to her murder in 1898 at the hands of the Italian anarchist Luigi Lucheni, through the lens of her growing obsession with Death as her marriage and her empire crumble around her at the turn of the century.