Appearing out of nowhere to horrify the quiet resort town of Sanibel Island, Florida, dozens of identical, ordinary-looking shoes float in on the tide and are washed up on the tropical beach --- each one with a crudely severed human foot inside. In short order, Agent Pendergast finds himself facing the most complex and inexplicable challenge of his career: a tangled thread of evidence that spans seas and traverses continents, connected to one of the most baffling mysteries in modern medical science. Through shocking twists and turns, all trails lead back to a powerful adversary with a sadistic agenda and who --- in a cruel irony --- ultimately sees in Pendergast the ideal subject for their malevolent research.