Peter Quint is just all kinds of trouble. On the most superficial level, he’s an evil spirit who’s come to haunt and/or possess little Miles. That alone would be enough to pin him as the villain of this story, but wait – there’s more!
Not only is he a menacing ghostly presence, he’s also a walking symbol for a whole passel of terrors. First of all, Quint stands in for the social threat of the lower classes. In life, he was an ambitious servant, who, we’re led to believe, was a bit too big for his britches. Mrs. Grose tells us that Quint didn’t know his place, and that he was given too much power – once the children’s uncle left Bly, Quint took control of the house and its inhabitants. Quint’s character represents the breakdown of the highly structured social hierarchy that existed in James’ day; while this may not seem so horrifying to us these days, it felt like a real threat back then.
Quint also represents another scary threat: sex. We know that he seduced the unfortunate Miss Jessel (their class difference also contributes to this menace; Quint is a destroyer of young ladies), and that he spent far too much time alone with young Miles. Quint is described as handsome but dastardly, and he is seductive and frightening in equal measure. Basically, Peter Quint stands for everything the Governess is afraid of, and this sense of menace is his most distinguishing characteristic.