On a hot and dusty Sunday in June 1872, 13-year-old Mary Secaur set off on her two-mile walk home from church. She never arrived. The horrific death of this young girl inspired an illegal interstate pursuit-and-arrest, courtroom dramatics, conflicting confessions, and the daylight lynching of a traveling tin peddler and an intellectually disabled teenager. Who killed Mary Secaur? Were the accused actually guilty? What drove the citizens of Mercer...