A plague is spreading through the city of Cray. Nobody knows its origin and nobody has discovered a cure. Cray is dying. Of glass.
As the city's ruling council resorts to increasingly desperate measures to maintain order, two people's lives are about to change. When the Keeper of the Cowhorn Tower witnesses a vast lens in the night sky, his work collating the city's scattered historical records takes on a significance he could not have imagined. And when Subadwan the Archivist is chosen to explore a land she never knew existed, she finds herself at the centre of a plot which threatens to shatter the very nature of reality.
And the glass plague advances.
