Between 1898 and 1912, families across the country were bludgeoned in their sleep with the blunt side of an axe. Some of these cases—like the infamous Villisca, Iowa, murders—received national attention. But most incidents went almost unnoticed outside the communities in which they occurred. Few people believed the crimes were related. And fewer still would realize that all of these families lived within walking distance to a train station. When celebrated true crime expert Bill James first learned about these horrors, he began to investigate others that might fit the same pattern. Applying the same know-how he brings to his legendary baseball analysis, he empirically determined which crimes were committed by the same person. Then after sifting through thousands of local newspapers, court transcripts, and public records, he and his daughter Rachel made an astonishing discovery: they learned the true identity of this monstrous criminal and uncovered one of the deadliest serial killers in America.