In the 1990s, a pre-internet called Usenet developed a bit of a spam problem. Hundreds of messages titled Markovian Parallax Denigrate were posted over the course of one day, but decades later something more interesting was discovered about them.
On December 17, 1967 Australian Prime Minister Harold Holt waded into the ocean for a swim while the rest of his party watched from the beach. He disappeared in the waves and was never seen again. Was it an accident, murder, suicide, or a well executed defection?
A New Jersey pastor and his lover were brutally murdered, their bodies found posed in ritualistic fashion beneath a tree. The most shocking crime of early 20th century America culminated in a trial that ended with a fizzle, with several suspects and no obvious answers.