The only other resident at Bly is housekeeper Mrs Grose. Which is why the governess becomes very agitated when she sights two other people - in the grounds, in the house itself; getting, it seems, ever closer to the children - and grows more agitated still when her descriptions prompt Mrs Grose to identify them: Miss Jessel, the governess's predecessor, and Peter Quint. Both dead. Mrs Grose recalls that Quint was a bad 'un, a man who held influence over the children, Miles in particular. The governess fears that Quint and Jessel's malign influence still threatens Flora and Miles from beyond the grave.
Plotwise, there's about enough for twenty-five pages. James, turning the English language into the world's longest paper-chain, constructs elaborate sentences, clauses within clauses, and the whole thing ends up five times that length. It's not an easy read and if you consider it mainly on narrative terms - story structure, development, denouement - it doesn't really go anywhere. It is, however, rich in atmosphere and even richer in ambiguity. This latter is the reason for its enduring status as a classic, both literary and as a work of genre fiction, and explains why it has proved so ripe for adaptation (an opera, theatrical productions, a story by Joyce Carol Oates reworking the material from the ghosts' point of view; four TV adaptations that I know of and at least as many movies). The ambiguities allow other writers - not to mention composers and directors - to bring their own sensibilities, perceptions and ideas to bear.
Having said that, every take on 'The Turn of the Screw' that I've come across has retained the supernatural element. I've yet to see (or read or hear) a version that approaches the material purely as a psychological study of the governess's gradually disintegrating sanity. This is one of the two accepted mainstream critical readings of 'The Turn of the Screw': the ghosts are in the governess's mind. The other reading is to take the genre trappings at face value: the ghosts are real and so is the threat to the children; when you go down this route, speculation follows as to whether some degree of possession hasn't already afflicted them, particularly Miles.
I should add that I'm deliberately oversimplifying the critical response to 'The Turn of the Screw' here, purely to contextualise the point I'm about to take - to whit, that most TV/movie adaptations go for a have-their-cake-and-eat-it approach by cherry-picking the most dramatically exploitable opportunities from both readings and amalgamating them into a melange of barely-contained hysteria served with a side order of sexual repression - but if you want to delve further into James's challenging novella, I highly recommend The Turn of the Screw: A History of its Critical Interpretations, an academic but very readable site that provides an historical through-line of critical thinking on the work.
Over the next two nights, I'll be looking at two very different takes on 'The Turn of the Screw': one all flickering candles and dark corridors, the other in modern dress; one buttoned-down, the other with added nudity. One an accepted classic, the other with few fans ... I'll be turning the screw, but will I be turning the tables?