Bran Yarrow loves the outdoors and adventure above all else. But when his mom's second marriage threatens to upend his life, Bran runs away from home. What he didn't expect is that his hideyhole would turn into a portal to a world entirely underground!
In the world of Cavernia, where glowing mushrooms and talking bats exist side by side, Bran is ready to finally go on the adventure he's always dreamed of. But everything is not as it seems. When a decades old conspiracy starts to reveal itself, Bran teams up with Blank, a talking slime who has more than a little sass, and Altamira, a sweet girl who looks like she came straight out of hell, to save his new home from destruction, all while figuring out the things that truly matter in his life.