Mum comes to take Maisie to her house for a few hours – supposedly so I can work. I wave them off at the door, noting my daughter’s vacant stare and a patch of dry, flaky skin on her forehead.

Five minutes after they leave, I head out to the car, the Linby House keys in my pocket.

Shaun obviously didn’t notice the keys were missing when he came back down from the loft and scooped the contents of his pocket back up from the worktop. And now I’ve told him I haven’t seen them, so he must assume he’s lost them elsewhere.

After I said I needed time to think about the house sale, he couldn’t get away fast enough.

‘We’re heading to Leicestershire for the afternoon tomorrow,’ he said by way of explanation for his haste. ‘Joanne has agreed that Piper can have the afternoon off school to look at a pony that’s for sale. She’s promised her another one when we move.’

He rolled his eyes and smiled, but I looked back at him blankly.

‘You’ll need to come over again soon,’ I said. ‘There’s something more important than a house sale that we need to talk about.’

He raised his eyebrows.

‘Maisie,’ I said. ‘She’s troubled. Someone is upsetting her, I’m sure of it. Surely you can see she’s fading away in front of our eyes?’

‘Right. If you say so.’ He backed away, as if I was exaggerating again. ‘See you soon, then.’

He clearly wasn’t interested in talking about the possibility that Joanne or Piper – or both – was responsible for systematically destroying Maisie’s self-esteem. That didn’t fit in with his nice clean break from the two of us.

I felt like shouting at him until he came to his senses, but I let him go.

I have other plans that may well prove to help my daughter.

By 3.20, I’m heading up the long, leafy driveway of Linby House. It’s impressive, I can’t deny that.

As the car reaches the top of the driveway, a large red-brick house looms in front of me. There’s a turret on either side, and a large glass balcony spans the top floor, overlooking fields and the neighbouring village of Papplewick.

I park up outside in a marked visitor spot. Judging by the numbered parking bays, the house looks to be divided into six apartments. I don’t know the number of Joanne’s apartment, but Maisie told me it’s at the top of the building.

I get out of the car and glance down at the keys in my hand. A sturdy-looking entrance door has a keypad and also a lock, so I would think one of the keys will be for that. The other should be for the front door of the apartment.

I walk around a decorative fountain, its water half frozen and trickling through. I’m just about to slide the key into the lock when the main door opens.

My heart feels like it has jumped into my mouth. What if I misheard the time and Shaun and actually he and Joanne were only just leaving now? But I needn’t worry. A young woman bustles out holding a baby and struggling with a large padded bag that I assume holds all the necessary paraphernalia one has to carry everywhere with a very young one.

‘Lifesaver, thanks!’ She beams as I hold the door open.

I allow it to click softly behind me and stand for a moment in the airy, calm entrance hall. The wooden flooring and high ceiling give the impression of space, although the area itself is not enormous.

I climb to the first floor and look down, out onto my parked car, from the large stained-glass windows. Up on the second floor, there are three doors and a final staircase. No lift here, no wonder Joanne is so slim.

I’m puffing a bit by the time I reach the top, but I’m gratified to see just one door. Number 6.

I raise the key to the lock and then, just to be safe, I knock. If they’re still home – which is unlikely, as there’s no car outside – I can say I found the keys on the floor at home and came over to return them.

No answer, so I slide the key in and turn it.

Inside, another short flight of carpeted stairs greets me. This takes me into the apartment proper. A very tasteful space decorated in neutral colours, with smooth wooden floors and lots of mirrors and pale textured fabrics.

There’s no time to delay. I know what I’m looking for, so I get straight to it.

All the doors are open, and I can see at once which one is Joanne’s bedroom. Simply decorated with an antique oak sleigh bed and built-in wardrobes, the view is mesmerising. Large picture windows look out over the grounds of the house and the fields beyond, the whole scene framed with beautiful mature oak trees.

Briefly I think about our own little patch of garden. Shaun and I loved it when we first bought the house. We regarded it as sizeable, a step up from the postage stamp we had at our first place.

He must stand and laugh about that now, as he soaks this view in each morning.

I look at the bed and look away again. It’s too close to home. I really don’t want to think about Shaun and Joanne entwined on here.

Turning my attention to the task at hand, I systematically search the drawers, but it’s soon apparent there is nothing that can help me here.

I leave the bedroom and glance into the room to my right, which is the main bathroom. Next to it is a small, neat office.

I pull at the top drawer of a small black filing cabinet and groan when I find it locked. I peer into a pen tub on the desk and smile. The so-called security systems people have are generally laughable. No wonder burglars have a field day in posh areas like this.

I open the drawer and feel obliged to Joanne for her immaculate organisation. Each suspended file pocket is neatly labelled: House, Car, Bank and Personal.

Sliding my hand into Personal, I retrieve a folder. I place it on the desk and slip my phone out of my pocket.

Inside the folder, I find a paperwork gold mine that answers a lot of questions and my suspicions feel validated at last.

Leafing quickly through, my fingers close on the last item in there: a small photograph. I stare at the image, trying to make sense of it, but there’s no time to ponder.

I take the required snapshots quickly and efficiently, then replace the folder exactly where I found it and make sure I close the drawer properly.

I leave the apartment exactly as I found it, and after listening at the door for a moment, and satisfied that nobody is out there, I step out and pull it closed behind me.

A couple of minutes later, I’m driving back through the leafy gravelled corridor that leads to the main road.

My mouth might be dry and my breathing is definitely erratic, but my mission is accomplished.

I now have what I need to find out a little more about my husband’s lover and her nasty little daughter. Between them I am certain they are destroying Maisie in the most calculated way.

The information I have gleaned here today might just help to prove that.