Book excerpt: A real-life murder mystery in turn-of-the-century London, and Scotland Yard’s “greatest detective of all time” who was determined to discover whodunit. By 1919, Det. Chief Inspector Fred Wensley was already a legend, having investigated the Jack the Ripper slayings, busted crime syndicates, and risked his life at the notorious Siege of Sidney Street. But the brutal murder of kindly fifty-four-year-old widow and shopkeeper Elizabeth Ridgley was an unexpected challenge in a storied career. Elizabeth and her dog were both found dead in her blood-spattered shop in Hitchin. But even in the early days of forensics, Wensley was stunned by the inept conclusion of local Hertfordshire police: it was a freak, tragic accident that had somehow felled Elizabeth and her Irish terrier. At Wensley’s urging, Scotland Yard proceeded with a second investigation. It led to the arrest of an Irish war veteran. The only real evidence: a blood-stained shirt. But the Ridgley case was far from over. Drawing on primary sources and newly-discovered material, Paul Stickler exposes the frailties of county policing in the years after WWI, reveals how Ridgley’s murder led to fundamental changes in methods of investigation, and attempts to solve a seemingly unsolvable crime.