On February 5, 1908, Kate Skinner, a 21-year-old unmarried barmaid in Brighton, England, gave birth to twin girls. They each had ten fingers and ten toes, but were joined back to back at the base of the spine. Freaks, monsters-that's what they were called. Mary Hilton, Kate's employer and midwife, adopted Violet and Daisy and promptly began displaying the babies as "Brighton's United Twins." Exhibitions at street fairs, carnivals, and wax museums...