In this, Butler’s last book, she returns to the notion of symbiosis so thoroughly explored in Lilith’s Brood, here with vampires rather than aliens. The book follows Shori, a young woman who awakens to horrible injuries, no memory of her life until that moment, and a fierce hunger. As with Lilith, Shori tests the limits of what it means to be human: both their stories argue that an expansion of those limits is a necessary precondition of our survival.