Isobel lives an isolated life in North London, where she works at a nearby library. She feels safe, so long as she keeps to her routines and doesn't let her thoughts stray too far into the past. But a newspaper photograph of a missing local schoolgirl and a letter from her old teacher send her spiraling and bring back the trauma of what happened years ago, when she was a pupil at The Schoolhouse.

The Schoolhouse was a 1970s experimental school where the usual rules did not apply. Life there was a dark interplay of freedom and adventure, violence and fear. It was here that Isobel learned that some truths should never be revealed. But try as she might, the truth is coming for Isobel, and everything and everyone she has tried to protect are now at risk.