"The wonder is I didn't see at once.
I never noticed it from here before.
I must be wonted to it—that's the reason.
In line 21, the man says something that the woman would probably scoff at, which only makes the guy seem more ignorant: He's amazed he didn't see what she had been looking at immediately.
He says, instead, that he's never before noticed "it" (we poor readers are still in the dark about what "it" is) from that particular spot on the stairs.
Why didn't he see it? Because he's "wonted to it." Wonted, in this case, means accustomed to, or used to. Basically, he's saying that he hadn't noticed what was bothering this woman so much because he's used to it—whatever it is.
This realization opens up a couple of possibilities:
For one thing, it tells us that this guy has lived here in this house for a while. He's used to the things he sees. So used to them, in fact, that he hardly notices them anymore.
And it tells us that maybe this woman is new to the house. She notices things he doesn't because she's not used to them.
The little graveyard where my people are!
So small the window frames the whole of it.
Not so much larger than a bedroom, is it?
Finally. The moment we've all been waiting for. We get the lowdown on what this "fear" is, over twenty lines later. Or we get the beginning of the lowdown, at least.
At a certain point on the stairs, the man tells us, we can look through the window and see the graveyard where his people, or his family and ancestors, are buried. The graveyard is so small that it's possible to see the whole plot through that one window.
The man casually comments that the graveyard isn't even much bigger than a bedroom. Now, we here at Shmoop don't like to think of graveyards in bedroom terms, but that's how he sees it. We're guessing that he's so used to this house, and to the graveyard outside the window, that seeing this graveyard is just like seeing a normal garden.
For the woman, though, it packs quite the punch.
There are three stones of slate and one of marble,
Broad-shouldered little slabs there in the sunlight
On the sidehill. We haven't to mind those.
But I understand: it is not the stones,
But the child's mound—"
Slowly but surely, the "fear" is being revealed to us. The man is describing the graveyard, where three of the stones are made out of slate and one out of marble, which are both common materials to use for gravestones. With only four gravestones, this is, as we've been told, a pretty small graveyard.
It's a little creepy the way he talks about these gravestones in lines 28 and 29, don't you think? He's almost affectionate towards them. He personifies them, saying that they have broad shoulders. Picture the gravestones as wide at the top, then narrowing on the way down, just like a man's torso would.
The way he says they're in the sunlight on the sidehill (note the alliteration of the letter "s" in these lines) makes the graveyard seem quaint, even pretty.
But just when we think we've figured out that it's the graveyard that's scaring the woman, the man tells us not to "mind," or worry about, the gravestones he has just described.
This seems a little dismissive of the people in his family who are buried there, and of the general creepiness of having a graveyard in the backyard (although that was fairly common in ye olden times).
But in any case, the man tells the woman that he "understands," and moves on to say that it can't be the stones that are bugging her so much. So what is? He sure is taking awhile to get to the point.
We get the answer (at last) in line 31. It's a child's grave that is really bothering the woman.
With the words "child's mound," we can start to construct the characters and the scene of this poem a lot more than we've been able to so far.
First, the word "mound" lets us know that this isn't a full-blown grave. There's not even a stone on it, as far as we know. This probably means that this isn't a grown child, but probably a baby, possibly a stillborn baby.
We can also guess, because the grave still is a "mound," that the dirt has been recently shoveled on top of it. The ground has not yet sunk back to level. It's a fresh gravesite.
With the information that the woman is upset about the child's mound, we can guess that these two characters are husband and wife.
The husband said earlier that he's used to seeing the graveyard, which implies that the wife is not used to seeing it. That means they're probably in a new marriage, and that the wife has just moved into her husband's home recently.