Raffa Santana is a healer, not a fighter. As a gifted apothecary, he has amazing instincts for unleashing the potential of magical-seeming plants. But his skills have failed to free the animals that the heartless Chancellor captured and turned against the people of Obsidia, directly threatening Raffa's friends and family.

Eight-year-old Jack, his seven-year-old sister, Annie, and Peanut the mouse ride in a tree house to the Amazon rain forests, where they encounter giant ants, flesh-eating piranhas, hungry crocodiles, and wild jaguars.

Hoping to return home after a winter in the Sudden Mountains so he can join his parents in the fight against the evil Chancellor, Raffa must use his apothecary skills while enlisting the help of human and animal friends to survive the journey.

When she finds the key to a secret passageway leading out of the walled city of Bridewell, twelve-year-old Alexa realizes her lifelong wish to explore the mysterious forests and mountains that lie beyond the wall.