This article explores the early modern understanding of the gut-mind relationship through a study of the beliefs and practices surrounding the hellebore plant in seventeenth-century England. Hellebore has been strongly associated with mental illness for most of recorded European history, and it is only during the past two centuries that it has lost this association. Taking a phenomenological approach, I demonstrate that the study of this specific plant, its representations, and its practices is significant not just to plant folklorists and medical historians but also to wider histories of culture, religion, emotion, and the body. The use of hellebore as a treatment for disorders of the mind reveals a fully embodied view of emotion in which the gut played a key role in shaping subjective experience. It also reflects a potently negative understanding of emotion as excremental matter, as something inherently impure, dangerous, and evil, warranting a violent remedy that was as punitive as it was therapeutic. By analyzing medical sources—herbals, pharmacopoeias, practitioners’ casebooks, and domestic receipt books—alongside devotional literature and religious polemic, I show that hellebore's symbolic importance was inseparable from its practical use as a treatment for mental illness, which depended upon an understanding of emotion and religious identity that accorded vital significance to the relationship between belly and brain.