Deepest, darkest / written and illustrated by William Ritter.

Enhanced descriptions from Syndetics:

The third adventure in the beloved fantasy series full of folklore and mayhem takes brothers Tinn and Cole on a dangerous journey to find their long-lost father.



"Cinematic adventure and hope amid darkness, flavored with silliness: a winner." -- Kirkus Reviews , starred review



Brothers Cole and Tinn are determined to solve a mystery almost as old as they are: What happened to their long-missing father?



Joseph Burton vanished without a trace, leaving the babies' mother to raise them--one human, one a goblin changeling--alone. Some say Joseph abandoned his family, others that he met foul play looking for a way to get rid of the changeling imposter. Cole is determined to learn his father's true fate, so he and Tinn set out on a dangerous quest to the deepest, most deadly limits of the Oddmire--with the help of Evie, expert on the creatures of the Wild Wood, and Fable, the indomitable half human, half fairy.



Meanwhile a shudder runs through the forest. Increasingly powerful earthquakes shake the land, sinkholes form, and the spriggans, trolls, and other creatures along their path speak of an ancient evil on the rise . . .



In the third book of the Oddmire series, New York Times bestselling author William Ritter takes readers on an unforgettable journey of family, fate, and a dangerous, magical forest.