Two siblings become increasingly frightened by their grandparents' disturbing behavior while visiting them on vacation.
 
According to statements made on Twitter, director M. Night Shyamalan prepared three different cuts of the film: one that was "pure comedy," another that was "pure horror," and a final one that "fell somewhere in between."  I guess I saw the "somewhere in between" version because the movie wasn't funny or scary.
 
FUN FACT:  Director M. Night Shyamalan does not make his customary cameo in this movie.