The Axe Murders of the Spencer Family

This episode has so many twists and turns that if it was a novel, someone on Goodreads would complain about it being "unrealistic". 
A whole family was murdered one night in the 1870s. The motive was clear, but the perpetrator was (and still is) a mystery. Though a trial ensues, the town decides to take matters into their own hands. 

Otherwise known as The Horsey Episode. 

Sources: 
1) https://johnbrassardjr.com/2020/01/11/the-spencer-family-massacre-part-1/ 
2) https://johnbrassardjr.com/2020/01/25/the-spencer-family-massacre-part-2/
3) https://khqa.com/news/local/family-of-five-brutally-murdered-in-clark-county-in-1877
4) https://www.mississippivalleypublishing.com/group-takes-another-look-at-125-year-old-murder-case/article_b57f4759-a9c7-5ef7-89f9-0be4783df114.html