Twelve-year-old twins Hugo and Kitty have an ultra-rare condition called heterochromia, which bestows them with different coloured eyes: one hazel, the other blue. On holiday in rural Australia, the twins befriend their solitary neighbour, Lucas, who has developed a powerful solar device he calls the Helios Book.

Lucas promises it will revolutionise global energy use. In a desperate attempt to escape those who would steal the Helios Book, the twins follow a fairy wren down a wombat burrow and into the mysterious world of Taara, a land plagued by a terrifying earthquake-like phenomenon called the Blurrings, and home to those who would take a nefarious interest in the twins' heterochromia.

The Helios Book is the Adventures of Alice in Wonderland for the Age of Extinction.