My review might annoy you. It might even anger you. I sometimes have that effect. So, before things devolve to that unhappy state, let me say up front that you are an impressive writer. Your prose is strong and assured. It’s clean and highly readable. No rookie blunders nor unintended howlers. You introduce two characters at the outset that we immediately want to get to know and you waste no time providing them with motivation that would seem to be ready-made for whatever plot you might cook up. Further, you never strand the reader in an ambiguous time flow, leaving them to wonder, Did this happen before that? Or, when am I, anyway? Readers have an unwavering sense of where now is, and they are quick to tag deviations from it in the narrative.

So, given all that, it could reasonably be asked, “What’s your problem, man?” It can be distilled down to four words:

Ya got no story.

Don’t get me wrong: things happen, characters are in motion, and there is genuine emotional interaction between those characters. But it’s not a story. It’s just a series of unrelated events, sort of like real life. Allow me to explain.

In the opening passages you do something quite effective: you let us know that we are in an alternate universe without calling attention to the fact or beating us over the head with a wealth of detail. Thus, as various elements are brought forth that further clarify the nature of this universe, we’re prepared, and they too fit seamlessly into the narrative flow.

When the younger sister loses her first tooth, her brother’s reaction, and hers, makes it clear that this represents something of far greater importance than our own hide it under the pillow and wait for the tooth fairy ritual. In your story, the loss of a first tooth signifies some significant rite of passage. What is the significance? Ya got me. You don’t tell us. But that’s the thing with alternate universes. We don’t need to know everything. We don’t need to know anything in particular. What we need is to see characters behaving and interacting according to the laws of this universe. You need to know, of course, but we can get by on the flimsiest of hints, as long as they remain consistent. You do this well.

We now learn that this significant milestone warrants a visit to the old lady on the hill. Again, what old lady? What hill? And why is she there? We have no idea. But by this time, it’s enough for us to recognize that our young characters know, and that they are eager for the encounter.

So at this point, with a minimum of effort, and seemingly without breaking a sweat, you’ve caused your reader to think, I wonder what’s gonna happen next. If you can get them thinking that, they’ll keep reading to find out.

Readers always come to a new story with a full measure of good will, and they trust that wherever you’re going to take them, it will have been worth their time and effort. When the story begins as has this one, that investment of time and effort would seem that it will prove well rewarded. But readers are a fickle lot. The second they begin to sense that their faith was misplaced, you’ll lose them and won’t get them back. For you, that moment is triggered about the time the old lady launches into her “story.”

I’ve mentioned The Readers and how they can be a fickle lot. You need to keep them in mind always; they might bring good faith to the table, but they also bring expectations, mostly based on your own text. In your set-up, you’ve given them ample cause to view the children, probably the little sister, as the main character. Main characters are the POV character, our access point to the psychological and emotional dimensions of the story. It is the main character’s story that becomes the core of the larger narrative, and our interest will be focused on her progress through whatever plot points you devise as she moves towards her goal. I nominate the little sister for this role because it’s her tooth, she is the reason they set out to visit the old lady in the first place.

When this new character makes her appearance, we are neutral in our assessment of her. We’re willing to take the children’s’ word for it and wait to see what happens. What happens, however, for no apparent reason, is she suddenly hijacks the role of main character for herself. Readers don’t like that. You’ve made them comfortable with a certain set of assumptions, and now suddenly they’re forced to readjust to what is essentially a new story. Worse, she makes no effort to fulfill her usurped role. Instead, she outsources it to a myth from the dim mists of time, one that, on repeated readings, appears to have no relevance to any of the threads you’d begun weaving in your set-up.

You need to recognize: regardless of its content, the old lady’s story is not part of your story. That unfailing sense of where now is that I’ve ascribed to readers will be sounding warning klaxons as they puzzle over where the story you’d sold them disappeared to. They’ll be looking at their watches, impatiently waiting for this unwanted detour to eventually take them back to that real story. Sad to say, few will see it through to the end, and those that do will be unsatisfied.

Here’s the actual template for your story:

Two children visit an old lady in the hills as a result of an important event in the life of one of them > she spends a long time talking > they all cry.

This is what will register on your readers’ NOW meter. Note what’s missing from this structure, after the inciting incident: problem > decisions > actions > complications > third act > resolution.

For the record, I checked out A Weight Worth Bearing in your portfolio, to make sure I hadn’t reached conclusions prematurely. I found similar issues: wonderful prose, the kind of prose that assures a reader that they’re in good hands, along with a narrative which, while far more realized than this one, still misses on closing the deal. You owe it to yourself to do some homework on the dynamics of story structure. The quality of your writing would seem to demand it.