Horror genre has to involve in the supernatural themes - the extradimensional, one would say - which is an artistic take at what our minds were not designed to properly seize in the current structure of things. That is why, it always remains a question without answer, the supernatural. Horror needs to end with mystery, while the mystery itself, is enough of a dread in proper respect. Horrors that eventually turn out to be all explainable and rational, are called 'thrillers'.