Henry James's 1898 novella is an exploration into the unknown, so it only goes with reason that a novel under this pretense would end mysteriously, with not one identifiable answer being revealed.
Completing a circle, and winding up back at the beginning, without any sure evidence to convince the reader of the truth or falsity of the supernatural occurrences is in itself a message. During the panel discussion, someone brought up what the point of this was. I cannot adopt the existentialist perspective and declare that the novel (or the film) does not matter. However, I think one has to dig in order to find that "point." The piece of fiction could simply be a lesson in futility; however, it seems that the adaptation to film omitted several aspects of this mystery.
The 1961 film adaptation, The Innocents, directed by Jack Clayton, is very blatant in its delivery of the ghostly figures. I think the film could have, in a way, been handled in a much similar fashion with its delivery, just like the novella. In the novella, the ghosts remain incredible and are never truly confirmed, yet it seems that for film, the decision to bring them into appearance was not so wise. In the best horror films (and this is purely my preference), the nature of the threat/monster/unknowns is better left unseen and hidden for the foremost portion of the film, if even shown at all. Once something is revealed, the nature of it is not so frightening anymore. I have no doubt that this film, and even more so, the novella it was adapted from, were both horrifying to people in their time. I must bring up another novel written in the same time period, which is The Strange Case of Dr. Jekyll and Mr. Hyde. It is a classic, and I think the nature of this piece of fiction is still timeless, much like The Turn of the Screw.
However, I found myself somewhat detached from and hypercritical of the cinematic adaptation, The Innocents because of the lack of mystery surrounding the ghosts.