It seems like an ordinary day when Tui and Kae, fourteen-year-old twins, get home from school - until they find their mother, Maia, has disappeared and a swirling vortex has opened up in her room. They are sucked into this portal and dragged down to Rarohenga, the Maori Underworld, a shadowy place of infinite dark levels, changing landscapes and untrustworthy characters. Maia has been kidnapped by their estranged father, Tema, enchanted to forget who she really is and hidden somewhere here. Tui and Kae have to find a way through this maze, outwit the shady characters they meet, break the spell on their mother, and escape to the World of Light before the Goddess of Shadows or Tema holds them in Rarohenga forever.