I take the stairs two at a time. The door to our bedroom is ajar. The curtains are still open and Mark, lying on the bed with a file on his chest and his mouth slightly open, is bathed in soft light. A snore catches in his throat before he falls quiet again. I gently fold the duvet over him, then retreat back out onto the landing. I can’t wake him, not if he’s this tired. He works so hard.

I glance at my mobile phone. It’s just after 7.30 p.m. If I want to get to Avonmouth before the sun sets I need to leave now. I cross the landing to Jake and Kira’s room and stand silently outside the door. Tinny dialogue drifts through the cracks. A second later Jake and Kira roar with laughter. The sound is so foreign, so wonderful, it makes my heart leap. They sound so happy. I can’t ask them to come and look for Billy with me.

I return to the living room and call Liz. She picks up on the second ring.

‘You all right?’

‘Yeah. I was just wondering if you fancied coming to the Lamplighters in Avonmouth with me.’

‘Now?’

‘Yes.’

‘Oh, sorry, mate. I’m in town. I’m meeting Caleb and his new boyfriend for a drink.’ She practically squeals the words ‘new boyfriend’.

‘He’s letting you meet him?’

‘I know! I’m under strict instructions not to do, or say, anything that might embarrass him so that’s basically me sitting mute in the corner for the whole night but yes, can you believe it?’

‘That’s great news, Liz.’

‘We could go for a drink tomorrow if you like? Why do you want to go to Avonmouth anyway?’

‘It doesn’t matter. I’ll tell you tomorrow. Enjoy your night.’

‘I will. Take it steady!’

I put down the phone and drop back into the armchair. The documentary has finished and a weight-loss programme has started. I flick through the channels. Images flash up on the screen and then vanish – a woman in the throes of labour, a father and son playing football, a pregnant woman, a family having dinner, a teenager in a hospital bed. I turn off the TV. The sudden silence makes my ears ring.

I pick up my magazine.

Put it down again.

I pick up my mobile and scroll through Facebook.

Pictures of cats. Pictures of food. Pictures of sunsets. Gripes about bad days at work, leaking showers, annoying neighbours and the government.

I close the app.

My foot tap-tap-taps on the floor as I look around the living room – at the photos of Jake and Billy on the mantelpiece, at the DVDs and books in the bookcase, at the framed print I bought Mark for our first anniversary.

Tap-tap-tap. Tap-tap-tap.

I can’t just sit here and do nothing.

I can’t.