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 Māori Underworld, a shadowy place of infinite dark levels, changing landscapes and untrustworthy characters.