Her baby is unresponsive, and as she turns her over, she sees that her face is blue and she doesn’t appear to be breathing.

Panic seizes Mary’s chest. She quickly lifts Charlotte out of the cot and immediately becomes aware of how cold she is.

‘Oh, dear God, no,’ she bellows when it suddenly becomes obvious to her what has happened.

She turns around and lays Charlotte on the bed. Her nurse training kicks in and she starts to administer CPR.

‘Start breathing, sweetheart,’ she pleads. ‘Please wake up. Please.’

But she doesn’t. And though Mary has spent enough time in hospital emergency rooms to know that she never will, for ten minutes she carries on hysterically pumping Charlotte’s chest and blowing air into her tiny mouth.

When she finally accepts that her daughter is dead, she lets out a scream that it more animal than human and collapses onto the bed beside her.

The tears flow and she’s swamped by a sense of loss that is so profound it feels like hot lead is flowing through her veins.

She knows that if she had found Charlotte sooner it might have been possible to save her. She could have kept her alive until the paramedics arrived, and once at the hospital the doctors could have worked their magic.

But she also knows that even then the odds would have been against Charlotte surviving, given that every year in the UK around two hundred babies die suddenly and unexpectedly.

It’s clear to her now that Charlotte is a victim of sudden infant death syndrome, or cot death, as most people know it. Her body temperature and the colour of her skin suggest to Mary that she passed away at least a couple of hours ago …while her mother was fast asleep only a few feet away.

The guilt she feels is overwhelming and it adds to the riot of emotions raging through her mind. She pulls her baby close and kisses her forehead.

‘I’m so sorry I went to sleep,’ she sobs. ‘Please forgive me, my darling. I beg you.’

Even through the turmoil in her head she knows she’s meant to call the police, but she doesn’t want to. She doesn’t want them to take Charlotte away. Not now. Not ever.

She will have to tell Robert that his daughter has died, though, and she can’t bear the thought of it. The news will destroy him and in all likelihood their marriage as well.

He’s bound to say it was her fault. That she should have been watching their baby.

It means she will have to lie and say it happened really quickly and there was nothing she could do. And she can’t possibly admit to being asleep.