Young Mollie traverses eerie, perilous lands to retrieve her baby brother, Thomas, from the Kinde Folke, malicious sprites who snatched him and left a hideous changeling in his place. When her adorable baby brother is replaced by an ugly, ill-tempered changeling, Mollie is determined to find the so-called Kinde Folke who took baby Thomas, return the changeling she calls Guest, and make them give Thomas back.