A woman discovers she has a rogue body part, one she’s never heard of. As she prepares herself for surgery to remove the offense, she travels to London and finds answers to her questions in unexpected places—a locked room in a museum where jars of Victorian body parts are stored, an early 19th century operating room in the attic of a church, and a diary by a woman whose husband dissected a rhinoceros in their flat. Along the way, she ponders the nature of disease, the unfortunate name given to her errant organ, and the marvels of modern surgery. This is the story of the last body part discovered—the parathyroid gland.