On a snowy January morning in 1889, a worried servant hacked open a locked door at the remote hunting lodge deep in the Vienna Woods. Inside, he found two bodies sprawled on an ornate bed, blood oozing from their mouths. Crown Prince Rudolf of Austria-Hungary appeared to have shot his seventeen-year-old mistress Baroness Mary Vetsera as she slept, sat with the corpse for hours and, when dawn broke, turned the pistol on himself. A century has transformed...