"The dangerous thing about spider light is that it hides things - things you never knew existed. But once you have seen those things, you can never afterwards forget them ..." The sleepy market town of Amberwood seems to offer peace and anonymity after a shattering and all-too-public tragedy in Antonia Weston's past. But as she struggles to re-build her life, she becomes increasingly fascinated by the macabre history surrounding her: the disused watermill, Twygrist, with its brooding darkness, and the now-vanished Latchkill Asylum where, a hundred years ago, the unfortunate inmates suffered gruesome fates. But Antonia's fascination with the linked histories of Latchkill and Twygrist has alerted someone from her own past. Someone who knows all about Twygrist's darkness. Someone prepared to use that knowledge to the most horrific effect ...