What exactly happened all those years ago when Granma had that car accident and lost her memory? Why is the man with the withered hands sneaking in and out of hospital rooms? And why is the policeman standing outside their house brandishing a . . . toilet brush? In this, the first in a series of three books about eleven-year-old Ivy and her fourteen-year-old brother Seb, we explore the mystery of the land beneath London, and why Ivy's family is so crucial to the future of life in both worlds.