The skinny girl in the photograph is wearing Lucy Bretherick’s clothes. Same shirt, same dress. Even the same socks and shoes. Identical, right down to the lacy frill at the top of each sock.

My head throbs. This is too much. I sweep the pictures off the sofa on to the carpet and press my hand over my mouth. I have to eat something or I’ll be sick.

The phone rings. I pick it up, manage no more than a grunt.

‘Did you switch your mobile off?’ a furious voice demands.

‘Esther. Sorry,’ I say limply. I must have forgotten to switch my phone back on when I left Corn Mill House.

‘It’s lucky I never listen to you, isn’t it? If I’d followed your instructions, I’d have phoned the police and made a complete tit of myself. What happened to calling me back within two hours?’

‘I’ll ring you back,’ I tell her, and slam down the phone.

‘So, you want to know what I think about everything apart from the infidelity bit. Right?’

I shovel more sauceless spaghetti into my mouth and make a sound that I hope answers Esther’s question. It took me fifteen minutes to tell her everything, then another ten to get her to swear on her life that she wouldn’t tell anyone, no matter what.

‘Funny, the infidelity is what I want to talk about most.’

‘Esther-’

‘What the hell were you playing at? That could have been it, Sal-your marriage over, your happy home wrecked, and for what? A few fucks with a man you hardly know? Your children’s lives ruined-’

‘I’m going,’ I warn her.

‘Okay, okay. We’ll discuss it another time, but we will discuss it.’

‘If you say so.’ I know Esther’s point of view is the correct one. It’s also easy, conventional, and it bores me rigid. ‘Didn’t I always say you’re more sensible than me?’ I try to make light of my newly confessed sin. ‘Proof if proof be needed.’

‘It’s not a joke, Sal. I’m actually shocked.’

Good. ‘Do you have anything to say about the rest of what I’ve told you? Or should I leave you in peace to consolidate your moral outrage?’

There’s a pause. Then she says, ‘Could the woman and girl in the photos be William Markes’ wife and daughter?’

Her words make me feel numb and wobbly, as if I’ve stepped off a roller-coaster in the dark. ‘Why?’

‘I don’t know.’ I listen as Esther chews her fingernails. ‘I just wondered if… I’m thinking of one family-the Markeses-trying to pass themselves off as another. I don’t know. I need two weeks on a desert island to think about it.’

‘Mark Bretherick doesn’t think his wife wrote the diary.’

‘Yeah. You said.’ She sighs. ‘Sal, isn’t it obvious? You and I can’t work it out in a phone call. You need to go to the police.’

‘The photos weren’t necessarily hidden,’ I say, stalling. ‘Haven’t you ever put a new picture in a frame and been too lazy to take out the old one? So you put the new one next to the glass and leave the old one behind it?’

‘No,’ Esther says flatly. ‘And especially not if one of the photos is of another girl wearing my child’s clothes. You’re sure they’re the same? Not just similar?’

‘All I know is they’re both wearing a dark green dress, a green and white striped blouse with a round-edged collar-’

‘Hang on. The dress is short-sleeved? If there’s a blouse underneath? ’

‘Yeah, it’s like a sort of tunic.’

‘It sounds like a school uniform,’ says Esther. ‘What colour shoes and socks? Black? Navy?’

‘Black shoes, white socks,’ I say breathlessly.

‘Hardly a casual Saturday-at-the-owl-sanctuary sort of outfit. Not that I’m an expert,’ Esther adds with distaste.

I put down my bowl of pasta, retrieve the pictures from the floor and look at them again. She’s right. What’s wrong with me? Of course it’s a uniform; it’s the green dress that put me off-it’s nowhere near as shapeless and institutional as most school tunics. Its short sleeves are fluted, the neck is shaped, and it’s got a belt with a pretty silver buckle. A uniform. It makes perfect sense. Every school in the county, like every parent in the county, takes its children on trips to Silsford Castle ’s owl sanctuary.

‘Sally? Hello?’

‘I’m here. You’re right. I don’t know how I missed it.’

‘You should still phone the police.’

‘I can’t. Nick’d find out about last year. He’d leave me. I’m not risking it.’ Please don’t say it. Please.

Esther says it. ‘You should have thought about that before you shagged another man. For a week.’ As if only a day’s worth of infidelity would have been less reprehensible. ‘This isn’t just about you, Sally.’

‘Do you think I don’t fucking know that?’

‘Then call the police! Today you were followed, yesterday someone pushed you under a bus. Do you still think it was Pam Senior?’

‘I don’t know. I keep changing my mind. One minute it seems so crazy and the next… She was so keen to help after it happened. It made me suspicious. Ten minutes earlier she’d made it pretty clear she hated me.’

‘Oh, come on,’ Esther says scornfully. ‘There’s no mystery there. She’s dim, isn’t she? She sounds it, from everything you’ve told me about her. A dim person would always instantly forgive an enemy who’d nearly died.’

‘Would they?’

‘Yes. Sentiment would triumph over reason. “She nearly died, so I have to like her now”-that’s what Pam will have thought. Bright people continue to hate those who deserve to be hated, irrespective of contingencies.’ Esther’s voice is full of pride, and I know she’s thinking about her boss, the Imbecile. I listen to her loud exhalations as she tries to calm down. She hates not being in charge. ‘Look, Nick wouldn’t necessarily find out,’ she says. ‘It’s well known that the police protect adulterous witnesses.’ She talks over my snorts of derision. ‘It’s true! Most of them are at it themselves. Cops are real shaggers-everyone knows that. They won’t even disapprove. All they’re interested in is getting the facts so they can do their job. If you tell them everything you know, they’ll do their best not to involve Nick.’

‘You have no way of knowing that,’ I say, and put the phone down before she can argue with me. I wait for her to ring me back but she doesn’t. My punishment.

All they’re interested in is getting the facts. What was the Alfa Romeo’s registration? I knew it this morning. I memorised it.

I’ve forgotten. In the hours between then and now, it has slipped out of my mind. Idiot, idiot, idiot.

I pick up the four photographs, take them downstairs and put them in my handbag. Then I go back to the lounge and throw the two wooden frames into the wastepaper basket. The chances of Nick noticing or asking about them are zero; for once I’m glad I haven’t got a husband who’s observant and on the ball.

I think about the police. Real shaggers. How observant can they be if they didn’t find the two hidden photographs? Assuming they were hidden. Surely the house was searched after Geraldine and Lucy died. Why didn’t anybody find those pictures?

I know what school Lucy Bretherick went to: St Swithun’s, a private Montessori primary in North Spilling. Mark… the man at Seddon Hall told me. I’d heard of Montessori, knew it was a kind of educational ethos, but I wasn’t sure what exactly it entailed, and didn’t ask because he clearly assumed that as a fellow middle-class parent I knew all about it.

I don’t, but I plan to find out as much as I can-about the school, about both girls whose photographs are in my bag, and their families. Tomorrow morning, as soon as I’ve dropped Zoe and Jake off at nursery, I’m going to St Swithun’s.

Police Exhibit Ref: VN8723

Case Ref: VN87

OIC: Sergeant Samuel Kombothekra

GERALDINE BRETHERICK’S DIARY, EXTRACT 3 OF 9 (taken from hard disk of Toshiba laptop computer at Corn Mill House, Castle Park, Spilling, RY29 0LE)