On a sunny Friday afternoon, beloved teacher Mrs Walker and her eight-year-old son wave goodbye to their friends in the school playground. But they never make it home ...

It's only been a week, but the bright little faces at the picture-perfect school I've stepped into have captured my heart. Their big doe eyes, their paint-covered fingers and clinging hugs. They've been through so much, with their favourite teacher and classmate still missing ...

I'm doing all I can to help them adjust, but I can't avoid the swirling rumours that say Cate Walker's charismatic husband, Oliver - our headteacher - is involved in her disappearance. The thought makes me shudder. But the more I find out about Cate, the more I wonder if she was also hiding a terrible secret ...

I'm determined to uncover the truth about what really happened. I have to protect these other innocent children from the same fate - it's my duty as their teacher.

That is, until an anonymous note turns up threatening me if I don't stop looking. Until my home is broken into while I sleep.

I know the longer I stay here, the more danger I'm in.

But whoever's trying to scare me doesn't know who I am - or why I'm really here.

Or just how far I'll go to protect the people I love ...