In August 1860, in a tidy terrace house in London's East End, wealthy widow Mary Emsley was found brutally murdered. The case made headlines across England, captivating Londoners in particular with its lurid details. The wheels of justice turned swiftly, condemning to death a man whose suspicious behavior belied an intriguing past…and whom many, including the great crime writer Sir Arthur Conan Doyle, believed to be innocent. In this page-turning account, Sinclair McKay examines the science of detection, early forensic techniques, and seemingly insignificant details of Victorian life—particularly in the poor and working-class neighborhoods of the East End—to create a vivid, complex portrait of the infamous murder. History buffs and readers fascinated by true-crime tales will devour this historical whodunit, as it strives to uncover the true murderer's identity once and for all.