[CrazyIvan]

Silence of the Lambs. Most horror movies are too silly to be scary to me (eek, eek, Jason has a weed wacker). Silence of the Lambs’ villains were realistic enough to be really out there. Time for a couple extra locks and some more ammunition.

I don't know if the movie is based on them, but there really
have been some psychopaths similar to the ones portrayed in
the movie.

[Erasmus]

I think that The Devil in the White City may make a great horror movie based on fact, if given a good screen treatment.

Hopefully, the movie (being brought to the screen by Leonardio DiCaprio) will combine the atmosphere of Ragtime with the historical prototype of Hannibal Lecter in the person of H H Holmes.

(Arguably, the other Lecter prototype would be Holmes' contemporary, Jack the Ripper.)