Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third Person (Omniscient)
Emily may be the star of this story, but our unnamed narrator likes to prance through the minds of a whole bunch of characters in The Mysteries of Udolpho. Take this piece of info from St. Aubert's mind:
He saw a frank and generous nature, full of ardour, highly susceptible of whatever is grand and beautiful […] (1.6.25)
That would be St. Aubert's private evaluation of Valancourt, BTW. The narrator hops right over to Em's mind a little later to get her take on loverboy.
We like to think of this narrator as an annoying little guy who holds back certain key pieces of information until he sees fit. Take the black veil episode, for instance. We know that "horror occupied [Em's] mind," but we don't know exactly why she's freaking out on us (2.6.46). It's just too terrible to tell. We don't know if we'll ever get to hear exactly what's beneath the black veil, but the narrator surprises us with that little tidbit at the story's close.