"The Moonlit Road" was one of the stories I remember reading in graduate school for the class on the 19th-century American gothic. (Among other things that are flexible in grad school, periodization is probably the most flexible of all. Never fall for the trick when someone asks when a particular century ended. The answer is always: we are still living in that century.) This story served as an example of Bierce playing with psychological horror themes rather than strictly supernatural themes. So here, the horror isn't a creature that is invisible, but a jealous husband, a murdered wife, a bereft orphan--and each gets their chance to tell their side.
That's one of the best parts of this piece, the structural split and uncertainty, moving from one sort of uncertainty to another. First, we start with the son's account--and, note, much of his account is from his father's account--which includes his unhappiness, his mother's death at the hands of an unknown assailant, and his father's disappearance for unknown reasons. So that's a story with several holes, some of which can be filled with each other: his father disappeared because he felt guilty for murder.
The second third is possibly the father's account--but only possibly. It's the account of a man about to commit suicide who tells what he knows of his story, which isn't much: he only remembers the last few years; has some strange connection to a number rather than a name; has a recurring dream of testing his wife's fidelity and killing her when he suspected she was unfaithful; and another memory of running from an apparition he saw on a moonlit road. So there's the answers, right? The husband did kill the wife; did see her ghost; and ran away in fear afterwards.
And the third section finally gives us the wife's version--as transmitted through a medium, which already makes it somewhat suspect. But the wife's version (if real) tells us several things: there wasn't anyone in the house with her--so we'll never know anything about that person or apparition that the husband saw; and she was killed in the dark without ever knowing who did the killing--so her final appearance to her husband wasn't a vengeful return but an attempt at connection. But that doesn't mean that her section is totally full of love. In fact, the wife/mother's section is full of lines that include several options, both love and hate, like:
Sometimes the disability [the fact that dead and living can't interact] is removed, the law suspended: by the deathless power of love or hate we break the spell--we are seen by those whom we would warn, console, or punish.Which of course leads to the question: if love or hate works, which is it here? Ultimately, even after we see all three versions, there are still questions that can't be answered here.