As Quebec City shivers in the grip of winter, its ancient stone walls cracking in the cold, Chief Inspector Armand Gamache plunges into the strangest case of his celebrated career.

A man has been brutally murdered in one of the city's oldest buildings - a library where the English citizens of Quebec safeguard their history. And the death opens a door into the past, exposing a mystery that has lain dormant for centuries... a mystery Gamache must solve if he's to catch a present-day killer.