Mae's beloved older sister, Abbie, has been missing for years. Mae has her theories about where Abbie might be. But nowhere in her wildest imagination do those theories encompass a fantasy world full of terrifying monsters, power-hungry nobles, and nefarious scientists. That is, until Abbie suddenly reappears in Mae's world. And not alone.

Mae, Abbie, and Kvido have nearly escaped death countless times, but that won't stop them from taking on the Zemětřasi to rescue their father. When they stumble across Petra Stoneheart, an old friend of Abbie's, Mae starts to learn more about the unfamiliar fantasy world she's followed Abbie through and about the sister she's been separated from for years.

Still no closer to finding her father and now hurt over her separation from Abbie, Mae finds herself on her own for the first time since arriving in Cimrterén. After finding new friend Drydon, they start a booming business selling Mae's "inventions." Skateboards, yo-yos, ice cream, and popcorn—totally unfamiliar in this new world—prove to be hot commodities. Once Mae's reputation of master inventor begins to spread, her new boss (a.k.a. her kidnapper) forces her to start inventing something far deadlier.

Mae's best friend Dahlia is still back in Indiana while Mae and Abbie go to The Other World, Cimrterén, to find their dad. But when Dahlia gets an unexpected visitor, he begins causing problems on campus. Between finals, missing her friend, and college parties gone wrong, Dahlia can't handle an other-worldly creature trying to find his way back through the gate.