Madeleine McCann.
The Delphi Murders.
The disappearance of Amy Bradley. She disappeared off a cruise ship in 1998. The most reasonable answer is that she was drunk and fell off the ship but there are so many weird details in the story that make you wonder.
Elisa Lam’s death, Hinterkaifeck murders, Villisca axe murder. These things make it hard for me to sleep at night and also whenever someone brings either of these three up I get goosebumps
Malaysia Airlines Flight 370.
It seems certain that a crime was committed, but it’s very unclear who committed it and why.