In the 1870s, two ambitious boys from different backgrounds, Jacques Rebière and Thomas Midwinter, find themselves united by a determination to understand how the mind works and whether madness is the price we pay for being human. As pioneering psychiatrists, their quest takes them from an English county lunatic asylum to the plains of Africa, the lecture rooms of Paris and the mountains of Austria and California. They are guided by Thomas's devoted sister, Sonia, and by an ex-patient, Katharina, whose arrival exposes profound differences between them. As the concerns of the old century fade and the First World War divides Europe, the two friends are compelled to a tragic revision of all that they have loved and pursued. Moving and challenging in equal measure, Human Traces explores the question of what kind of beings men and women really are.