On a cold day in 1667, a renegade physician named Jean Denis transfused calf's blood into one of Paris's most notorious madmen. In doing so, Denis angered not only the elite scientists who had hoped to perform the first animal-to-human transfusions themselves, but also a host of powerful conservatives who believed that the doctor was toying with forces of nature that he did not understand. Just days after the experiment, the madman was dead, and Denis was framed for murder. A riveting account of the first blood transfusion experiments in 17th-century Paris and London, Blood Work gives us a vivid glimpse of a particularly fraught period in history a time of fire and plague, empire building and international distrust, when monsters were believed to inhabit the seas and the boundary between science and superstition was still in flux. Amid this atmosphere of uncertainty, transfusionists like Denis became embroiled in the hottest cultural debates and fiercest political rivalries of their day. As historian Holly Tucker reveals, transfusion's detractors would stop at nothing not even murdering Denis's patient to outlaw a practice that might jeopardize human souls, pave the way for monstrous hybrid creatures, or even provoke divine retribution. Taking us from the highest ranks of society to the lowest, from dissection rooms in palaces to the filth-clogged streets of Paris, Blood Work sheds light on an era that wrestled with the same questions about morality and experimentation that haunt medical science to this day.