So I pass him. For a second the distance between us narrows to half a metre. He could grab me if he chose to, but he doesn’t. I keep going. I think – but can’t be sure – that there is the lightest touch of his fingers through my hair as I fly by. My trainers squeak the way they did the last time I took these stairs, up to Eliza’s room on the first floor, where I have been before.

Below, I can hear the police officer’s voice. ‘Hiya.’

Hiya, I think. Who says Hiya in these circumstances? Clearly, this police officer, who continues to speak. ‘Zac Hunter, the time is 09.27 and I am arresting you on suspicion of the murder of Jane Miller. You do not have to say anything, but it may harm your defence if you do not mention . . .’

I strain to listen. Zac does nothing to alert the police that I am here, but I know I have a couple of minutes at best before the house is swarming with detectives.

I try to look at the room as Eliza would. The first thing I notice is that the collage of photographs from her dressing table is gone. One of her precious things, and she seems to have taken it, despite Zac saying she didn’t pack before leaving last night. There is nothing interesting or personal in her drawers, which are filled with cashmere and silk.

At the bottom of her wardrobe is a small, fireproof deed box. I heave it onto her bed. It’s locked, but it’s the kind of flimsy thing meant to stop it from popping open in a fire rather than to deter thieves or a husband. I grab the battery-operated lock pick gun from my bag. After a few seconds of vibrating buzz, I have the lock open.

When I lift the lid, the first thing I am faced with is a photograph of Zac holding Alice. Alice is about six months old, and Zac is looking sideways at her, solemnly, while she giggles at the photographer. Alice is so like the newborn picture of my baby. My baby, wrapped in Milly’s blanket, with her copper hair and its beautiful streak of white. If they used age progression technology on the photo I have of her and stopped at six months, it would be identical to this one. I slip the photo into my bag. I will cut Zac out later.

The other thing in the deed box is an A4-sized plastic wallet. It is labelled ‘Alice – Important Identity Documents’. It isn’t Zac’s writing, so it must be Eliza’s. I stash the folder in my bag, too. As I do, something makes me turn towards the bedroom door.

Standing in the opening is a man. ‘Hello, Holly,’ he says.