‘It’s the blue tint to her skin. What happens to the heart, and the skin, if someone dies from a cardiac arrest, it’s the same as what happens with suffocation or strangulation. The heart continues to pump blood around the body for at least a couple of beats, but that blood doesn’t have as much oxygen, so it’s less pink. That’s why her skin has the blue tinge – the blood beneath it is deoxygenated.’

Tess nods. ‘Correct. Plus, the eyes are bloodshot.’ I nearly ask how she can know this, but realise she must have prised them open to look before we got here.

Maxine says, ‘Can Helen see her right ankle, please, Tess? You’ll need to go round to the other side of the bed, Helen.’

The oval is there, on the outer side of the lower calf, though I’d already half-glimpsed it. A smoky purple circle the size of a two-pence coin, slightly above the ankle bone. A bruise like a black star sapphire, perfectly cut, and set against the blue-tinted skin.

I am staring at that oval. Maxine is staring at me. ‘I’m not expecting you’d recognise her face in the circumstances, but have you seen the mark before?’ she says.

The room is starting to spin. I can taste bile. The last time I tasted that was when I woke in hospital after it happened.

‘No,’ I say.

‘You’re sure?’ she says. ‘It doesn’t remind you of anything?’

Three years ago, looking at the photo in Zac’s bedside table, I’d wondered if it was a tattoo.

‘It’s a birthmark,’ I say. ‘A dark circle, that’s all.’

‘I’d say it’s very distinctive,’ Maxine says. ‘Would you say that too, Tess?’

‘I would.’

‘Then I will defer to your expertise. Am I free to go?’ My breathing is getting faster. The room is starting to spin. I am so hot. My back is soaked, just as it was during the night sweats after her birth.

‘We’ve come across a photograph,’ Maxine says. ‘On the hard drive of a laptop that someone took a great deal of trouble to copy for us.’

I know who that someone is. That someone is me, and though I’ve never been told exactly what was on the drive, I have guessed.

‘There were indecent images and video footage on that drive – I can assure you it has all been carefully protected.’

I look at my feet. My eyes are welling up but I am determined not to cry.

‘One of the relatively innocuous images is of a woman lounging by a pool. Her birthmark is identical to this one.’

I take a few small steps, unhurriedly, towards the door. ‘I asked if I am free to go.’ I am practically choking.

‘Of course,’ Maxine says.

I am out of the room. I am on the landing. I am halfway down the paper-covered stairs.