The insidious Fleet Street barber slit his first throat in an 1846 "penny dreadful," one of those gaudy serialized novels that gleefully offered thrills and gore to sensation-hungry Victorians. TitledThe String of Pearls, it told of Sweeney Todd, whose shop stood next to St. Dunstan's Church, just a few blocks from the Royal Courts of Justice. On this site, he robbed and murdered hundreds of customers. To dispose of their remains, he carried them...