Rocio, a Maya Mam girl, lives in the mountains with her mother, who is pregnant and her granny. Due to an early delivery from her mother, Rocio is stuck with caring for a herd of sheep, the first time she has done it on her own. Playing in the mountains she loses one of the sheep. Looking for it, she will lose the rest of the herd. In the midst of this tragedy, Rocio will have to face her innocence, conquer her fear of fog and learn that freedom entails responsibility. Nature will teach her that you do not have to defeat your fears, you just have to experience them. The Greatest House in the World is a story of children -which we all are- when facing fears, the unknown, the uncertain... the fog.