In the winter of 1971, graduate student Willa immerses herself in a sensory deprivation tank for a routine psychological experiment. The hallucinations and delusions she experiences in the tank are considered normal side effects, but the sudden ability to speak fluent French is not. Each time she enters the tank, she becomes more convinced the hallucinations are actually someone else's memories. Her boyfriend dismisses her delusions and resulting anxiety and depression as proof that she is having a psychotic break. But what if her new abilities mean something more? Set in Wisconsin during the social turmoil and budding psychological science of the early 1970s, and inspired by actual events, Willa's pursuit of the source of her visions and fluency in French (a condition called xenoglossia) unearths an unlikely archaeological discovery and a shocking truth that changes her life forever.