This book identifies and names the phenomenon of metagnosis: the experience of newly learning in adulthood of a long-standing condition. It can occur when the condition has remained undetected (e.g., colorblindness) and/or when the diagnostic categories themselves have shifted (e.g., ADHD). More broadly, it can occur with unexpected revelations bearing upon selfhood, such as surprising genetic test results. This phenomenon has received relatively scant attention, yet learning of an unknown condition is frequently a significant and bewildering revelation, subverting narrative expectations and customary categories. In addressing the topic this book deploys an evolution of narrative medicine as a robust research methodology comprising interdisciplinarity, narrative attentiveness, and creating a writerly text. Beginning with the author’s own experience of metagnosis, it explores the issues it raises—from communicability to narrative intelligibility to different ways of seeing. Next, it traces the distinctive metagnostic narrative arc through the stages of recognition, subversion, and renegotiation, discussing this trajectory in light of a range of metagnostic experiences, from Blade Runner to real-world midlife diagnoses. Finally, it situates metagnosis in relation to genetic revelations and the broader discourses concerning identity. Proposing that the figure of blindsight—drawn from the author’s metagnostic experience—offers a productive model for negotiating such revelations, the book suggests that better understanding metagnosis will not simply aid those directly affected but will also serve as a bellwether for how we will all navigate advancing biomedical and genomic knowledge, and how we may fruitfully interrogate the very notion of identity.