Dr. John Haygarth knew that there was something suspicious about Perkins’s Metallic Tractors. He’d heard all the theories about the newly patented medical device—about the way flesh reacted to metal, about noxious electrical fluids being expelled from the body. He’d heard that people plagued by rheumatism, pleurisy, and toothache swore the instrument offered them miraculous relief. Even George Washington was said to own a set. But Haygarth, a physician who had pioneered a method of preventing smallpox, sensed a sham. He set out to find the evidence.