Kara Khan's life consists of secrets: the secret of her three-month disappearance from school last winter, the secret reason for the many scars on her face, the secret of the existence of the Crane King, the Wire Mistress, the Lady of the Streets and other dangerous and bizarre creatures. But the most terrible secret of everyone - her twin sister Parva, Kara's counterpart in another world, in London-beyond-Glass - the abode of monsters and miracles hidden under the surface of the bustling metropolis. A place where the spirits of wild trains scatter along the train tracks, and the streets are illuminated by light blue dancers with glass skin and sparkling veins. A place that cannot be forgotten.