Sixteen-year-old Jacques Rebière is living a humble life in rural France, studying butterflies and frogs by candlelight in his bedroom. Across the Channel, in England, the playful Thomas Midwinter, also sixteen, is enjoying a life of ease-and is resigned to follow his father's wishes and pursue a career in medicine. A fateful seaside meeting four years later sets the two young men on a profound course of friendship and discovery; they will become pioneers in the burgeoning field of psychiatry. But when a female patient at the doctors' Austrian sanatorium becomes dangerously ill, the two men's conflicting diagnosis threatens to divide them—and to undermine all their professional achievements. From the bestselling author of Birdsong comes this masterful novel that ventures to answer challenging questions of consciousness and science, and what it means to be human.