The Price family, about whom McGuire has written many books, includes many different sorts of humanoid beings with special powers and they fight against bad cryptids. Normally, they fight against "cuckoos", creatures from another dimension who are embedded into a human family as children and then kill them when entering adulthood, beginning a life of controlling unsuspecting humans with their psychic powers. Oh, and cuckoos also all love math, which is related to their ability to move between "dimensions". Indeed, Sarah Zelaby is a cuckoo, she has psychic powers, and she does love math, but having been adopted by the Price family saved her from becoming a monster herself.

At the end of the previous book, Sarah biological mother forced her to manipulate an equation that would transport the cuckoos to another dimension, but would kill Sarah, the Price family, and all life on Earth. Instead, she figures out how to save the day. Doing so, unfortunately, carried them and the university campus they were on to another universe, and erased any memory of her from the minds of her cousins.

This book picks up where that one left off. In the other universe, Sarah learns a lot about her race, the Johrlac, and their mathematics. (There is another "good" cuckoo there with them from whom she learns some things she did not previously know. Moreover, members of their ancestor race once also visited the planet they find themselves on, leaving behind stories and powerful equations.) But she has to work hard to convince her family to trust her again. This is especially painful in the case of her cousin Artie because in the last book they finally had confessed their love for each other, though of course he no longer remembers that or even who Sarah is. Also, she has to figure out how to get them all back to Earth, hopefully without dying in the process.

In narrating the book, Sarah does reveal some of her thoughts about math. For example;

I don't think I'm giving away too much if I tell you that her solution to the problem involves getting six white boards, a bunch of dry-erase markers, and some Sharpies.

"Why Sharpies?" you may ask. I'll let Sarah explain:

I would classify this book as "young adult" fiction, with an entirely unsubtle focus on the interests of teenagers, their crushes and their fandoms. And, it doesn't say anything particularly deep, meaningful, or interesting about mathematics. But, it is a fun book to read and math certainly plays a major role in it.