I check my handbag for my phone … yup. Keys … yup. Wallet … where is my wallet? I’m hunting for it when my eye alights on a letter in the rack, addressed to me.

I pick it up, intending to take it upstairs when I go back to look for my wallet, but then two things happen at the same time.

The first is that I feel the bump of my wallet in my jeans pocket and realise where it is. The second … the second is that I notice the letter has a Salten postmark.

My heart begins to beat a little faster, but I tell myself, there’s no reason to panic. If it were something from the police it would be franked, not stamped, surely, and would look like business correspondence – typewritten, in one of those envelopes with a plastic window.

This is something else – a brown A5 envelope, through which I can feel several sheets.

The writing isn’t Kate’s. It’s neat, anonymous block capitals, quite unlike Kate’s generous looping scrawl.

Could it be something from the school? Photos from the dinner, perhaps?

I hesitate for a moment, wondering whether to tuck it back into the rack and deal with it when I get back. But then curiosity gets the better of me and I hook a finger in the flap and rip it open.

Inside there’s a sheaf of papers, three or four sheets perhaps, but they seem to be photocopies – drawings rather than letters. I shake them out, looking for a top sheet to tell me what this is about, and as the pieces of paper flutter to the floor, it feels like a hand wraps round my heart and squeezes, so hard that there’s a pain in my chest. The blood drains from my face, and my fingertips are cold and numb, and I wonder for a moment if I am having a heart attack – if this is what it feels like.

My heart is thumping erratically in my breast, and my breath is coming sharp and shallow.

And then there’s a sound from above and an instinct of raw self-preservation takes over and I fall to my hands and knees, scrabbling for the pictures with a desperation I cannot even try to hide.

Only when they are back inside the envelope can I try to process what has happened, what I have seen, and I put my hands to my face, feeling the hot flush on my cheeks and a pulse beating hard in the pit of my stomach. Who has sent these? How did they know?

Suddenly it is more urgent than ever that I get out, talk to Fatima and Thea, and with hands that shake I shove the envelope deep, deep into my handbag and yank open the front door.

When I step into the street I hear a noise from above, and I look up, to see Owen and Freya standing by the open window upstairs. Owen is holding Freya’s pudgy little hand, and as he sees me turn, he waves it in a solemn goodbye.

‘Thank God!’ he says. He is laughing, trying to stop Freya from diving out of his arms. ‘I was starting to think you were planning to spend the whole afternoon in the hallway!’

‘S-sorry,’ I stammer, knowing that my cheeks are burning, and my hands are shaking. ‘I was checking the train times.’

‘Bye-bye, Mummy,’ Owen says, but Freya jerks against him, kicking her fat little legs, wanting to be put down, and he bends and lets her go. ‘Bye, love,’ he says as he straightens.

‘Bye,’ I manage, though my throat is tight and sore, as if there is something huge and choking there, stopping me from speaking or swallowing. ‘See you later.’

And then I flee, unable to face him any longer.

FATIMA IS SITTING at a table at Le Pain Quotidien when I arrive, and as soon as I see her, tense and upright, her fingers drumming the table, I know.

‘You got one too?’ I say as I slide into the seat. She nods, her face pale as stone.

‘Did you know?’

‘Did I know what?’

‘Did you know that they were coming?’ she hisses.

‘What? No! Of course not. How can you ask that?’

‘The timing – this meeting. It seemed a little … planned?’

‘Fatima, no.’ Oh God, this is worse than I had thought. If Fatima suspects that I was involved in this … ‘No!’ I am almost crying at the idea that I could have had something to do with this, and not have warned her, protected her. ‘Of course I didn’t know anything – how can you think that? It was a total coincidence. I got one too.’

I pull the corner of my own envelope out of my bag and she stares at me for a long moment, and then seems to realise fully what she’s suggesting, and covers her face.

‘Isa, I’m sorry – I don’t know what I was thinking. I just –’

A waiter comes over and she breaks off, staring at him as he asks, ‘Can I get you ladies anything? Coffee? Cake?’

Fatima rubs a hand over her face, and I can see she is trying to order her thoughts and is as shaken as I am.

‘Do you have mint tea?’ she asks at last, and the waiter nods and turns to me with a smile. I feel my face is fixed, false, a mask of cheerfulness over an abyss of fear. But somehow I manage to swallow against the constriction in my throat.

‘I’ll have … I’ll have a cappuccino, please.’

‘Anything to eat?’

‘No, thank you,’ Fatima says, and I find myself shaking my head in vehement agreement. I feel like food would choke me now, if I tried to swallow it.

The waiter has disappeared to get our drinks when the entrance door flings back, the bell jangling, and Fatima and I both glance up to see Thea, wearing dark glasses and a slash of red lipstick, looking wildly around her. Her gaze fixes on us and she gives a kind of start and comes across.

‘How did you know?’ She shoves the envelope under my nose, standing over me. ‘How the fuck did you know?’ She almost shouts the words, the envelope in her fingers trembling as she holds it out.

‘Thee – I –’ But my throat is closing against the words, and I can’t force them out.

‘Thee, calm down.’ Fatima rises out of her seat – palms outstretched. ‘I asked the same thing. But it’s just a coincidence.’

‘A coincidence? Pretty fucking big coincidence!’ Thea spits, and then she does a double take. ‘Wait, you got one too?’

‘Yes, and so did Isa.’ Fatima points to the envelope sticking out of my bag. ‘She didn’t know they were coming any more than we did.’

Thea looks from Fatima to me, then puts the envelope back in her own bag and sits down in the free seat.

‘So … we have no idea who sent these?’

Fatima shakes her head slowly, but then says, ‘But we have a pretty good idea where they came from, right?’

‘What do you mean?’ Thea demands.

‘Well, what do you think I mean? Kate said she destroyed all of … of these kinds of pictures. Either she lied, or these came from the school.’

‘Fuck,’ Thea says vehemently, so that the waiter who has come to hover, waiting for her order, slides unobtrusively away to wait for a better time. ‘Fucking cunting twatting wank-badgers.’ She puts her head in her hands, and I see that her nails are bitten to the quick, blood speckling the torn skin around the edges of her fingers. ‘Do we ask her?’ she says at last. ‘Kate, I mean?’

‘I think not, don’t you?’ Fatima says grimly. ‘If this is a kind of blackmail on her part, she’s gone to the trouble of disguising her handwriting and sending them anonymously, so I hardly think she’s going to fess up the moment we ask her if she sent them.’

‘It can’t be Kate,’ I burst out, just as the waiter comes back with our drinks, and we sit, scarlet-cheeked and silent while he sets them down and takes Thea’s order for a double espresso. After he has melted away, I say, more quietly, ‘It can’t. It just can’t – what possible motive could she have for sending these?’

‘I don’t like the idea any more than you do,’ Fatima snaps back. ‘Shit. Shit, this is all such a mess. But if Kate didn’t send them, who did? The school? What possible motive could they have? Times have changed, Isa. Judges don’t condemn schoolgirls as no angels any more – this would be an abuse scandal, plain and simple, and Salten House would be right at the centre of it. The way they handled the whole business was shocking, they’ve got almost as much to lose as we have.’