"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 ..."
Antonia Weston has come to the sleepy market town of Amberwood in search of peace and anonymity after a shattering and all-too-public tragedy in her life. But shortly after her arrival, a series of disturbing incidents occur - incidents that eerily echo a past she is trying to forget.
As Antonia 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. Memories of Latchkill still linger: memories of how, when the autumn dusk - the 'spider-light' - fell, no one would dare walk past its gates. Because a hundred years ago, people lost their identities inside Latchkill's walls. People such as the innocent Maud Lincoln, jolted out of that innocence by a brutal plot.
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 in the most horrific way ...