This chapter examines the four ‘late’ novels that are the peak of Penelope Fitzgerald’s achievement as a writer: Innocence, The Beginning of Spring, The Gate of Angels, The Blue Flower. Each novel is, at least superficially, a work of historical fiction in that it is set in the past: in 1950s Italy, in revolutionary Russia, in Edwardian England, and in late-eighteenth-century Germany respectively. But history is decidedly not the defining feature of these novels. Rather, as this chapter shows, all four works are characterized by their bold experimentation with narrative form and style, reflecting an intense concern with profound questions of body, mind and spirit that culminates in Fitzgerald’s haunting masterpiece, the story of the idealized yearning of the German Romantic poet Novalis both for Sophie von Kühn, his ‘heart’s heart’, and for revelation. Through close analysis of Fitzgerald’s methods of research, composition and editing, this chapter proposes fresh ways of thinking about the stylistic means by which these late novels create fictional worlds that expand to fill the reader’s imagination, and even appear to possess an existence independent of the novels themselves.