Sonja helped me wash the first morning I decided to leave the comfort of the sofa. She ran a bath and helped me to get in, then sat with a coffee on the toilet seat as I swished the soap around. When I was ready to wash my hair she pushed wads of cotton wool smeared with Vaseline into my long-suffering ears and then sat on the edge of the bath and held a plastic cup over each ear while I used the shower to rinse off the suds. I fingered the scabs and the stubbled skin, which itched. She waited until I was dressed and back downstairs before kissing me absently and leaving for work.

I went downstairs and sat in the study looking through my diary, beginning to plan work again, pencilling in dates and times for materials to be delivered, for a team to start work. I reached for the text-phone to contact Ian and saw its light already flashing. The Type-Talk operator spelled out that it was my mother calling to tell me Ellen was dead. I put the phone down and went back into the living room, where I undressed and lay on the sofa again, pulling the duvet tight over my scarred head.

When I sat in the York café with Ian and asked him if he liked Sonja, he said he couldn’t answer because he didn’t know her. And I realise that in many ways I don’t either. Sonja has said, and maintains to this day, that her synaesthesia is not a disability. On this point she is forceful, some might even say aggressive. Is it a disability? I don’t know and I can’t begin to guess. I have phenomenal vision — and that is how I see the world. My mother has an acute mind, so sharp she could cut herself and she did. And that’s how she interprets the world — as mental constructs to be taken apart, examined and reassembled. Sonja? I don’t know. I don’t know how she sees the world. Are there no constants? Nothing she can accept as a given, a priori, as my mother would say? There has to be - otherwise she’d have to relearn everything she knows at every moment of waking. Am I the constant for Sonja? I rather think I must be. Unchanging and unchanged. Did she feel my fear of change when I first touched her breast? And, if so, what did it taste like? How did it sound? I’ve spent a lifetime trying to touch her heart and I think, now, that the organ that has always responded is her brain.

Merboy spent his last summer diving, bowling, thundering through water. The E tang de Cazeaux was his playground, the campsite his fishing waters. He woke at dawn every day, slipped on T-shirt and shorts and went down to the water. The campsite had no showers, only one tap, so he washed in the lake with every other child there. He learned not to wake his mother until the dented grey 2CV van came to the site, bumping over tree roots, crushing needles and scenting the air with croissants, brioches, baguettes, grands pains and pine. Then he’d run back to the tent, unzip the door and shake his mother to wakefulness. She’d yawn, fumble in her bag, then give him some franc notes, which he crumpled in his hand as he ran after the van, yelling, a stream of French children following and he looked back and grinned. Sometimes he smacked a toe on a tree root and fell to the sandy, needle-strewn floor with a yelp, only to pick himself up again to chase his own tail of followers. The bread man recognised Merboy after a few days and gave him a free baignet every time he arrived, panting, at the van’s open doors.