Normally I’d say, ‘Don’t be silly, I’ll help!’ and we’d clear away companionably and pick over the evening and start laughing over something or other.

Not tonight.

I get ready for bed, feeling a bit numb, and I’m still lying there, totally rigid, wondering what on earth I do next, how on earth I proceed … when Dan finally gets in beside me.

‘Well, that went well,’ he says.

‘Yes.’ Somehow I manage to speak. ‘The lamb was delicious.’

‘They’re a fun crowd.’

‘Yes.’

There’s another long, weird silence, then Dan suddenly says, ‘Oh. I need to send an email. Sorry.’

He gets out of bed and pads out of the room in his bare feet. And for ten seconds I lie still, my mind trying to self-soothe. Dan is always sending emails. He’s always getting out of bed with some sudden late-night thought. He’s a busy man. It doesn’t mean anything. It really doesn’t mean anything …

But I can’t help it. My suspicion is like a desperate hunger; I have to obey it. Without making a sound, I swing my legs round, stand up and move silently to the door of our bedroom. The door of Dan’s study is open and the light is on. I lean forward noiselessly until I glimpse him, and feel another profound shock.

He’s standing in his study, tapping away on a phone I’ve never seen before. A Samsung. What’s that phone? Why does he need two phones? As I watch, he drops it into a drawer and locks it with a little key. It’s on the same key ring as his house keys. I never even knew he had that little key. I didn’t know he kept a drawer of his desk locked.

Why does he need to lock a drawer? What’s he hiding from me? What?

For a few moments, we’re both motionless. Dan seems transfixed by his thoughts. I’m transfixed by Dan. Then he suddenly turns and in fright I leap backwards, skittering silently away. I’m back in bed within ten seconds, the duvet pulled right over me, my heart banging furiously.

‘Everything OK?’ I ask as he gets back into bed.

‘Oh, fine.’

And I don’t know if it’s my desperate optimism surfacing, or my belief in giving everyone a fair chance, but I can’t rest until I’ve given him an opportunity to make this all OK again.

‘Dan, listen.’ I prod his shoulder until he turns, his face all tired and ready-for-sleepish. ‘Seriously. Is everything all right? Please. You look so stressed. If there’s anything, anything wrong … or worrying you … I mean, you would tell me, wouldn’t you? You’re not ill, are you?’ I say with a sudden gasp of horror. ‘Because if you were …’ Tears have started to my eyes. For God’s sake. I’m a nervous wreck.

‘Of course I’m not ill.’ He stares at me. ‘Why would I be ill?’

‘Because you seem so …’ I trail away desperately.

Because you were hugging Mary. Because you’re hiding something. Because you feel pinned in a corner. Because I don’t know what to think.

I gaze at him silently, willing him to see the words in my eyes. To react. To feel my pain. I thought we were psychic. I thought he would pick up on my every fear and reassure me. But he seems impervious.

‘I’m fine,’ he says shortly. ‘It’s all good. Let’s get some sleep.’

He turns over and within moments he’s breathing the heavy, regular breaths of someone who was so tired, they couldn’t hang about being awake any longer.

But I don’t. I lie awake, staring at the ceiling, my resolve hardening. Because I know what I’m going to do now. I know exactly what I’m going to do.

Tomorrow I’m going to steal his keys.

THIRTEEN

I’ve never stolen anything before. I feel so guilty I don’t know what to do with myself. I swiped Dan’s keys while he was in the shower and put them at the back of my underwear drawer. Now I’m hovering round the kitchen, wiping things that don’t need wiping, talking to the girls in a false, high-pitched voice and dropping spoons every five minutes.

‘Where are my keys?’ Dan comes, scowling, into the kitchen. ‘They aren’t anywhere. Tessa? Anna? Have you taken Daddy’s keys?’

‘Of course they haven’t!’ I exclaim defensively. ‘You probably just … misplaced them. Have you checked your jacket pockets?’

I turn hastily away before he can see the tell-tale blush in my cheeks. I would so not make an arch-criminal.

‘I had them.’ Dan is rummaging through the fruit bowl. ‘I had them.’

‘Yes, but we were all distracted by the guests, weren’t we?’ I say, deftly inserting a plausible reason for him to have lost them. ‘Just use your spares for now. I’m sure your proper set will turn up.’

‘I’m not using my spares,’ says Dan in horror. ‘I need to find my keys.’

‘It’s only for now,’ I say soothingly. ‘Look, here are your spares, in the cupboard.’

I double-checked the spares before I pinched his proper keys. So in some ways, I would make a good arch-criminal.

I can see Dan is torn between two huge yet opposing principles: Never admit defeat when something’s lost; and, Don’t be late for work. At last, making an impatient noise, he grabs the spares. Between us we chivvy the girls into their school sweatshirts and check their book bags and at last all three of them are out of the house. As Dan is closing the car door, I call out, ‘I’ll have another look for your keys before I leave,’ which is a genius stroke, because 1. if Dan unexpectedly returns, it explains why I’m in his study, 2. it deflects suspicion away from me, and 3. I can now ‘find them’ and leave them on the kitchen table, job done.

Let’s face it, I would make an excellent arch-criminal.

I watch as the car pulls away. I wait another five minutes, just in case. Then, feeling totally surreal, I tiptoe upstairs, not even sure why I’m tiptoeing. I hesitate for a moment on the landing, trying to stay calm, then slowly venture into Dan’s study.

I know exactly where I’m heading, but I pretend to myself that I’m just having a general look round. I shuffle through some papers about a planning decision. I examine a brochure from a rival office-construction company. I discover an old school report of Anna’s, in Dan’s in-tray, and find myself reading comments on her handwriting.

Then, at last, my pulse beating quickly, I find the little key on his key ring. I stare at it for a moment, thinking, Do I really want to do this? What if I find …?

The truth is, I don’t know what I’ll find. My mind won’t even go there.

But I’m here. I’m on a mission. I’m going to see it through. At last, swiftly, I bend down and unlock his secret desk drawer, my hand trembling so much that I have to try three times. But then I’ve got it open and I’m staring at what’s inside.

I’m not sure what I was expecting to find – but it’s the phone. The Samsung phone I saw last night. Just that, nothing else. I take it out, thinking wildly, Wait, what about fingerprints? and then, Don’t be ridiculous, this isn’t CSI. I press in Dan’s usual passcode and get straight in. Clearly he never expected me to find it. Which kind of comforts me. And kind of doesn’t.

It’s a pretty new phone. There are only twenty-four texts on it, back and forth. As I scroll down, I see they’re all to the same person – Mary. And I just stare, unable to process the enormity of what I’m seeing. It’s the nightmare, worst-case scenario.

My shoulders are rising and falling. My brain is shouting panicky messages at me, like: What? And: Does that mean …? And: Please. No. This is wrong. This has to be wrong.

And, almost worst of all: Was Tilda right, all along? Did I bring this on myself?

I can feel rising tears, mixed with rising incredulity. And rising dread. I’m not sure yet which is winning. Actually, yes I am. Incredulity is winning and it’s joining forces with anger. ‘Really?’ I feel like shouting. ‘Really, Dan?’

Everything else, I could rationalize. The moods … the familiar vibe between Dan and Mary … even the hug. But not this. Not these messages in black and white.

Gd to talk in 5.

10 am Starbucks?

It’s ok have distracted S.

Today was a bit tricky.

At home can’t talk

Remember PS factor

Going insane today she is NUTS

11 am Villandry

Running late, sorry

Thank God for you

I read all twenty-four messages twice. I take photos of everything with my phone, because … just because. Might come in useful. Then I put the Samsung back with my fingertips, feeling as though it’s contaminated. I shut the desk drawer, lock it carefully, check it again and back away, as though from the crime scene.

On the landing, I look around, feeling dazed, as though seeing our house for the first time. Our home. Our little nest, with its wedding presents and prints we bought on holiday and photos of the girls everywhere. All this time I’ve spent trying to make it cosy, make it hygge, create a place for us as a couple to retreat from the world. Now I look at my stupid candles and throws and carefully placed cushions … and I want to shred them all. I want to destroy them and throw them on to the street and yell, ‘OK, well, fuck you, then, Dan, FUCK YOU.’

Dan doesn’t want to escape with me. He wants to escape from me. Maybe it was our session in the secret garden that triggered a sudden latent passion for Mary. Maybe this is all really new and exciting for him. Or maybe she’s the latest in a long line of extra-curricular affairs that I’ve been too blind to see. Either way: sixty-eight more years of marriage? Sixty-eight more years of me and Dan together? It’s a joke, a terrible, horrible joke, and I’m not laughing, I’m crying.