In the summer of 1953 maverick neurosurgeon William Beecher Scoville performed a groundbreaking operation on a twenty-seven-year-old epileptic patient named Henry Molaison. The operation failed to eliminate Molaison's intractable seizures, but it did have an unintended effect: Henry was left profoundly amnesic, unable to create long term memories.The story of Patient H.M., as he came to be known, is the story of how we came to understand memory, and better understand ourselves. Scoville's grandson, award-winning journalist Luke Dittrich, takes us on a journey through the history of neuroscience, from the first brain surgeries in ancient Egypt to the fraught debate between surgeons over lobotomy operations on the twentieth century; from the gleaming laboratory analysing Molaison's disembodied brain, to the archives of the decrepit New-England asylum where his grandfather first developed a taste for human experimentation. Dittrich's compelling, kaleidoscopic investigation confronts unsettling secrets in his own family history, and reveals how the bright future of modern neuroscience has dark roots in the forgotten history of psychosurgery, raising ethical questions that echo into the present day.