When he learns of his diagnosis of advanced prostate cancer at age 71, Marsh, a neurosurgeon in London, is shocked. In one moment, he has crossed the line from doctor to patient. Marsh is beset by fears and concerns, and he also reflects on his own shortcomings as a caregiver to others. As in his earlier memoirs, “Do No Harm” and “Admissions,” Marsh’s exploration is intimate, insightful, witty and deeply moving.