Imagine that you’re in New York, with a successful career and a brand new engagement ring on your finger.

You miss your family, back in England, but that isn’t something you dwell on. Life is good!

And then imagine receiving a telephone call from your mother, telling you that your sister has gone missing.

What do you do?

Beatrice comes home.

And although her mother and her sister’s friends are able to accept what the police tell them has happened to Tess, Beatrice cannot. And so she begins to investigate her sister’s life, searching answers to explain what has happened, and why.

This story unfolds in a series of letters that Beatrice writes in her head to Tess. Wonderful letters. She talks of the past, of what she is doing, of what she is feeling.

The letters are such an effective device. They paint complex, vivid and utterly real pictures of the relationship between the two sister. They provide a moving account of a mother and her only surviving child realigning their relationship.They speak painfully clearly of the many stages of grief, of how it changes you, and of how difficult it is to put a life back together after a shattering loss.

Two sisters, and their mother. Real, complex, believable people to care about.

Emotionally, this novel is pitch perfect.

I’m afraid that the crime story rather lets it down. It was compelling and it raised some interesting questions, but the science didn’t ring true for me, and the complexity of the investigation just didn’t sit well with the emotional story.

If only the story of what happened to Tess had been a little simpler, had reached a different conclusion, this could have been a far finer novel.

As it was, the conclusion was striking – not so much a twist as a revelation that makes you rethink things you have read – was striking, but it didn’t feel quite right. I’m afraid I felt that maybe I had been cheated.

I’m holding on to the emotional story, but letting go of the crime story.

And I’m hoping that Rosamund Lupton can get the balance just a little bit better next time. Because then she really could write something very, very special.