Chapter 5 considers the implications of modernist efforts to rethink notions of gender and creative autonomy for our understanding of genius. Although some writers and artists imagined androgyny as something a man and woman could achieve together, the same does not appear to have been true of genius, which remains for the modernists a phenomenon exhibited or embodied by individuals. I contend that the modernists’ own practice of cross-sex collaboration challenges this conception, as evidenced by two examples: the play Cathleen ni Houlihan, by W. B. Yeats and Lady Gregory, and the novel Under the Volcano, written by Malcolm Lowry with significant input from his second wife, Margerie Bonner Lowry. Neither of these masterpieces could have been realized by just one of its coauthors alone, yet no member of either couple thought of that couple itself as “a genius.” This limitation on the conception of genius came with significant personal costs and misrepresents the true nature of the writers’ powerful displays of joint creativity. Genius, I conclude, is not solely the provenance of individuals but an invaluable human capacity that can draw strength from both male and female participation.