What we have here is the predecessor of the ID channel, however Robert Stack has a far creepier narration style than anything that ID could hope for. He presents himself as both a scary and deadly serious narrator, and an authority on whatever it is the episode was about.
On top of that, unlike ID, it tried to cover the entire range of the mysterious, appealing as much to the true crime crowd as it does to the Ancient Aliens crowd as it does to the Histories Mysteries crowd as it does to the basic conspiracy theory crowd.
Each episode had enough to appeal to a multitude of people, making it the ultimate series in its genre.
