People don't vanish into thin air, but it sometimes seems that way. Australia has a reputation for mysterious disappearances, but folk go missing everywhere, and families all over the world are left fearing the worst.Sometimes foul play is afoot: a serial killer snatching victims off the street, or a stalker with a score to settle. In those cases, it can be decades before evidence of a crime comes to light.The fear of sinister figures lurking in the shadows has inspired generations of horror movies. The most chilling, as you're about to hear, are based on real events. These cases are the ultimate true crime mysteries.