Dyatlov Pass Incident
If you like this sort of thing, the Unresolved Mysteries subreddit [0] is a great resource. Some plausible theories include avalanches and military experiments [1] [2].You could waste many days reading through Wikipedia's Unusual Articles [3]. If you like aliens, here are two worthwhile reads:https://en.wikipedia.org/wiki/Barney_and_Betty_Hillhttps://en.wikipedia.org/wiki/Travis_Walton_UFO_incidentGood luck sleeping with the lights off tonight :)[0] https://www.reddit.com/r/UnresolvedMysteries/
[1] https://www.reddit.com/r/UnresolvedMysteries/comments/1u031h...
[2] https://www.reddit.com/r/UnresolvedMysteries/comments/2q5bih...
[3] https://en.wikipedia.org/wiki/Wikipedia:Unusual_articles