Paola is a scientist. She loves space, physics, weather, the brain — all the facts that make sense of the world.

Yet the middle schooler comes from a tradition that believes in the unexplained. Her mother reads tarot cards, consults curanderas and warns her away from the river, lest a vengeful La Llorona capture Paola like the other girls who have vanished over the years.

Paola rejects her mother’s admonitions, which she deems hopelessly embarrassing. When she starts to have spooky, prescient dreams and her friend Emma disappears by the river, Paola starts questioning what she thinks she knows.

Tehlor Kay Mejia explores it all in "Paola Santiago and the River of Tears" (Rick Riordan Presents/Disney-Hyperion, $16.99), her first book for middle graders. She’ll discuss the book Thursday via BookPeople.

"I’ve always been fascinated by the ways women are demonized in folklore and myth, and La Llorona loomed so large in my experience of that growing up that it was a natural entry point for me," Mejia said in an email interview. The La Llorona legend warns of a woman who haunts waterways searching for children after she drowned her own.

"I’m a little like the book’s heroine, Paola, in that I like to dig into the things that scare me, so I wanted to push past the obviously spooky exterior and see if I could get to the heart of the story and what aspects of womanhood were twisted to create this legend," she said.

Mejia has long written fierce, female-centered stories for a young adult audience (late middle school to high school students): "We Set the Dark on Fire" and its sequel, "We Unleash the Merciless Storm," followed one girl’s rebellion against the patriarchal society in fictional Medio. She relished the pivot to a middle grade audience (late elementary to early middle school students).

"I think in YA, we’re very focused on breaking out of the world we’ve known. A lot of the adventure portions of the story involve a big departure from the trappings of the child’s life you’re leaving behind as you enter adulthood," she noted.

"With middle grade, the transformation occurs within and alongside the confines of a child’s life. It’s more about learning to be yourself and push against your too-small boundaries while knowing adulthood is still so far off. I find both those transitions so interesting, so I love writing for both age groups."

Paola also deals with everyday racism. That was part of writing authentically about her community, Mejia says.

"I wanted the book to feel like home to other Mexican and Mexican American kids, to show that even though we have these obstacles, we also have community, and storytelling, and food and culture and joy. So much life in a marginalized community is about that contrast, and it would have been doing a disservice to the bravery and perseverance of Latinx kids to pretend they’re not overcoming these issues (and more) every day," she says.

"Paola Santiago" comes from "Percy Jackson" series author Rick Riordan’s Disney imprint. Riordan chooses books that meld action and mythology like "Percy" but spotlight cultures that aren’t as frequently represented in kids books and are written by authors from those cultures. Past titles include Kwame Mbalia’s "Tristan Strong Punches a Hole in the Sky," which won a Coretta Scott King honor.

Mejia, a "lifelong ’Percy Jackson’ fan," says publishing with the imprint is exactly what she’d dreamed of when she first heard about the concept.

"When I heard Rick had grown up in Texas and was familiar with La Llorona’s story, I knew it was fate — I’m a little like Pao’s tarot-card reading mom in that way," she said.