It's history's most famous unsolved crime spree. In 1888, a serial killer who came to be known as Jack the Ripper gruesomely murdered five prostitutes in London's Whitechapel district. More than 100 men, from Lewis Carroll to Queen Victoria's grandson, have since been labeled suspects, and the guesswork has spawned an entire field of study, known as "Ripperology." Now, a new book turns the speculation on its head, by arguing that Jack the Ripper was actually a woman.