Between 1898 and 1912, families across the country were bludgeoned in their sleep with the blunt side of an axe. Jewelry and valuables were left in plain sight, bodies were piled together, faces covered with cloth. Some of these cases, like the infamous Villasca, Iowa, murders, received national attention. But few people believed the crimes were related. And fewer still would realize that all of these families lived within walking distance to a train...