As if a trapdoor has opened beneath your feet and you’re falling through it. One minute everything’s fine, you’re coasting along just as you have done for years. The next minute you’re dropping, plunging, plummeting into the dark. You can’t see the ground, can’t break your fall. Everything around you is falling, too. Everything you’ve built.

And this is where it starts: with a little blue numeral indicating three unread items in Messenger.

I clicked on it. At the top of the screen were new messages to and from someone called CoralGirl.

Message me later when you can x

Need to be careful this week like we discussed

Remember to delete messages as soon as you’ve read

I scrolled down to yesterday’s string of back-and-forth messages, reading up from the bottom. The first one was a seven-word message from Sean that stopped my heart.

Can’t stop thinking about what you said x

I meant every word

Need to talk to you again

Does K suspect anything?

She has no idea. But I can’t go on like this

We’ll decide when we’re in France. Figure out what to do

I need to tell her. Soon

We talked about this. Better a secret.

I know but I feel so bad for lying to K

I couldn’t bear to read the messages but I couldn’t stop either, couldn’t take my eyes off the little words on the screen, each one another bomb exploding under my marriage.

I scrolled back up and read them again.

Does K suspect anything?

She has no idea. But I can’t go on like this

Something splashed onto the phone’s screen and I realised that I was crying.

In that moment, it was as if I didn’t know my own history any more, my own story. We’d had one life, our life together, and within a second it felt like fiction. I hadn’t even realised I was playing a role. With my hand shaking, I clicked ‘View profile’ on CoralGirl’s account. A generic silhouette instead of a picture, generic email. Lives in London. Female. That was it.

I hastily marked the latest messages as unread, then locked his phone and shut it back in the drawer. Sitting on an unfamiliar bed, in a strange house, in a foreign country, staring blankly at the wall in front of me.

Cold and hot. Angry and tearful and sick with betrayal.

Falling backwards into the dark.

A dozen questions, then a dozen more.

Was it serious?

Why had Sean done this?

How could I have misjudged him so badly?

But the biggest question – who is she? – was already half-answered, the clue right there in tiny black letters on a screen.

We’ll decide when we’re in France

France.