A spine-tingling debut about grief and obsession, with a shocking twist of an ending.

Marianne is still reeling from the death of her sister when she starts to exhibit some strange physical symptoms. Each day, it seems, her body betrays her a little bit more, and no one can explain to her what is going on.

Then a doctor offers her the hope of recovery - a stay in Nede, an experimental health retreat deep in the Welsh countryside. Surrounded by high walls and cut off from the outside world, it sounds like exactly what Marianne needs.

Desperate to get her life back on track, she leaves everything behind - her stressful job, her unsatisfactory relationship, her troubled family - hopeful that she finally has a chance to heal. Yet all is not as it seems at Nede. Yes, the surroundings are idyllic. Yes, the other residents seem happy. But something doesn't feel right.

Marianne begins to lose control as she obsessively revisits the days and weeks leading up to her sister's death. But now she must confront a more immediate threat: a dark experiment that appears to be taking over her mind, her body and her precious memories.