The story centres on Ailsa, the headteacher of a Norfolk school. One day a staff member presents her with a mobile phone confiscated from one of the pupils. The phone contains an explicit video clip which has gone viral. The girl filmed on the clip is very clearly Ailsa's daughter.

Why has she taken part in this video? She is an excellent student and well behaved at home. Who is at fault?

As the story progresses, we realise that nothing is ever black and white. Many different events lead to this phone video being made. Innocent, complicated or well-meaning decisions, and private and personal motivations, have far different outcomes from those originally intended.

This is a gripping and terrifying thriller which is very much of our time. There are so many perils of this internet era. It is so easy to mess up, the author says, it's amazing it doesn't happen more often.

Read my interview with author Fiona Neill here.