There’s a light, blinking red on the dashboard. I’m running out of petrol. I need to stop. I need to find a garage. The buzzing in my head dims as I pull in to a large Tesco but, instead of parking by one of the petrol pumps at the service station, I drive into the car park and turn off the engine. I pull a packet of wet wipes out of the glovebox and wipe my hands, the steering wheel and my jeans. I work methodically; wiping, then dropping the used wipes into an empty plastic bag until I am clean. Then I reach for my bag. It’s on the passenger seat. Underneath it is a photo album and an A4 diary, opened at today’s week.

Mark’s appointment book.

Why have I got Mark’s appointment book? He normally keeps it on his desk in the corner of the living room. Did I take it? He’s methodical about diary-keeping, entering everything into this book as well as his phone, just in case his phone dies or is stolen. I open it and run a finger down the appointments he’s got listed for today:

9.45 a.m. – Fallodon Way Medical Centre, 3 Fallodon Way, BS9 4HT

10.45 a.m. – Nevil Road Surgery, 43 Nevil Road, BS7 9EG

11.45 a.m. – Horfield Health Centre, Lockleaze Road, BS7 9RR

2 p.m. – Gloucester Road Medical Centre, BS7 8SA

Where am I? I open my handbag and take out my phone. It’s 2.30 p.m., Friday 14th August. Five hours have passed since I went into the garage to look for the screwdriver set and …

I see an image in my mind of a photo album, the photos defaced and scrawled on, but that’s it. That’s all there is.

I must have gone back into the house and picked up Mark’s diary but I don’t remember doing that. Or getting into my car and driving. Oh my God. I could have killed myself. Or someone else.

I look back at the phone and open Google Maps. The red location dot blinks several times, then the map comes into focus. Tesco Lime Trees Road. So I am still in Bristol. I enter one of the postcodes from Mark’s diary into the app and a tiny red line appears, connecting my location with the address I’ve just entered. It’s three minutes’ drive away. I zoom in on the location and turn on street view. That’s where I was just parked, outside Gloucester Road Medical Centre. Did Mark ring me and ask me to bring his diary to him? It’s the only logical explanation but it only takes twenty-five minutes to drive from Knowle to Gloucester Road. What else have I been doing in the last five hours?