Mrs. Oliphant was popular during her lifetime but is rarely read today; at most, one can find her work in collections of old ghost stories, or online. The Open Door is one of her tale's of the supernatural, and follows the same sort-of pattern that many other Victorian ghosts inhabit: the sympathetic spirit. It is rather more of a story about the emotions and suspense of finding and helping a ghost, then the terror of that ghost itself (although, of course, that does play a role).
In basic, Mortimer's son, Roland, mysterious sickens at the beginning of winter. He begins to hear a wailing of pure despair and a voice at an old ruin nearby his home, and tasks his father with finding out how to help the spirit in it's distress. Deathly afraid of ghosts, as all but a few people seem to be in this tale, but also a nonbeliever, Mortimer eventually finds, first, that the ghost is real, and second, that, through the local minister, he can usher the unknown from our world to the next.
This story is ripe with thematic depth. There are many rungs to this wheel, one might say. On one, we see the relation between skepticism and human behavior. Throughout the story, we see odd (or seemingly-odd) things left uninvestigated merely because those who would be curious are afraid their reputations could be soiled by the attempt. The scientific means by which something could be revealed is thus restrained by the conventions of human behavior. This extends even to our protagonist's first two meetings with the ghost, in which he describes his doings as looking very like a scene in which a murder would most likely occur (and him, of course, the murderer!). The story is also seemingly about the supremacy of the believer over the skeptic, with our friend Dr. Simson, at the end, flatly denying the existence of the ghost, and explaining away everything with somewhat flimsy or nonexistent solutions. It is hard not to associate the minister's ability to actually solve the problem with Simson's inability. Symbolically, Simson brings a taper, our protagonist a lantern, and the minister an old-fashioned lantern (with no means of shutting the light out)--Mortimer's brings more light than the taper, the minister's lantern more than Mortimer's. I think it is important to note here that our author seems to purposefully remove any strict doctrine from the priest, making him more of a 'believer' in general than that of a dogmatist. Further, the story seems to be about a father-son connection. This impels the protagonist to do what he does, and allows for him to face his fears concerning the mere idea of a ghost, and eventually gain a level of empathy for the ghost like unto the empathy he feels for otherwise normal human beings. (The priest, as well as Roland, our protagonist's son, are alone capable of seeing through the mists of personal fear, toward the true heart of the issue, from the beginning.) In some sense, then, this story is about humanizing the spirit, instead of fearing it (with, in my experience, many Victorian stories pursuing the latter).
Anyway, true to Mrs. Oliphant's abilities, this is an expertly told story that was well worth the reading. I didn't quite like some of the gendered language and coded action, but otherwise great.