Though brave and resourceful, he has a heart condition that threatens his life. This summer, Felix is spending his vacation in Costa Rica.

At a spot called the Divide — where the waters that run down to the Pacific and Atlantic oceans separate — Felix tumbles into a magical backwards world where mythical creatures are real and human beings are only a legend. There, Felix meets Ironclaw, an enormous brazzle, and Betony, a kind-hearted tangle-girl. Felix and his newfound friends set off on a thrilling quest to find a cure for Felix' illness and a way for him to return home.