He laughed. ‘Maybe. A bit. It’s just that you’ve only ever really seen me here, with Cerys, being grown up and responsible. I’m only thirty-six, Holly. I’m not ready for settling into Grandad things, all mint humbugs and dodgy knitwear . . . I’d like you to see me a bit more as I am.’

‘Oh yes? And how is that?’

He thought for a while, tapping the silver thumb ring against the steering wheel in a salsa rhythm. ‘Actually, now I come to think about it, I’m not entirely sure.’

‘Well then.’

The office in Leeds was in The Headrow, city centre, not the lock-up on a trading estate that I’d been expecting. It was surprisingly salubrious and, while Kai proved his identity to the satisfaction of the smartly dressed receptionist (another surprise, I thought all PIs worked alone and the dames were strictly decoration), I read Country Living magazines. It was like a private health clinic.

Eventually a door opened and Kai was ushered into another office. He motioned at me to stay where I was, but I could see he was shaking as he went inside.

I chatted to the receptionist. It’s always been part of my job, getting on with people, and I long ago learned that the quietest, most overlooked people are often the ones with the story to tell, particularly when they are the ones that open the mail and answer the phone. Her name was Laura and she’d been doing the job for five years, and when we’d got over the fact that I didn’t know Brad Pitt or Johnny Depp, and she’d got out the biscuit tin, I found out quite a lot more about the letter Kai had received.

‘All done over the phone,’ Laura dunked a chocolate biscuit. ‘The lady didn’t want to travel.’

‘So, when did she get in touch?’

‘Dunno. Quite a while back, I think. You’d have to ask Donald. I talk to so many people who are looking for someone . . . It’s sad sometimes. I mean, Donald is good, but . . . you can hear it in their voices, they know the person never wants to speak to them again, but they still want him to find them.’

‘And it’s Kai’s mother?’

Laura wrinkled her nose. ‘Can’t tell you. Sorry. Confidentiality and all that,’ she said in a voice loud enough to have been heard in the adjoining office, but followed it by nodding vigorously until the top of her biscuit fell in her tea.

I looked at the closed door. The silhouetted dark shape that was Kai was visible through the frosted glass. He looked hunched, as though he had his head in his hands.

‘Poor bloke,’ I said.

‘Tasty though.’ Laura grinned at me. ‘You two . . . you know, a couple?’

‘No,’ I said. ‘He’s a friend. Well, sort of. His daughter and I are friends, he’s . . . Do you know, I’m not sure what he is?’ Yes, he’d kissed me like he’d wanted to rip my clothes off, and although we’d not got down to the horizontal tango we’d certainly managed more than a few steps of the vertical rhumba.

‘I see. You’re, like, the nanny.’

Before I could correct her misconception, the office door opened and Kai came out looking as though someone had yelled in his face. He was holding a folded piece of paper.

‘Let’s go, Holly,’ even his voice was pale.

‘Good luck,’ Laura whispered. ‘And don’t forget, they always fall for the nanny.’

I could feel Kai shivering like a wet dog. As we walked through the crowds to get back to the car he kept stopping, turning his head, following people with his eyes and after a while I worked out that he was watching parents with children. Mothers, specifically, pushing overloaded buggies or chatting to toddlers whose normal wide-eyed overactivity had been pushed to almost unbearable levels by the Christmas lights hanging overhead and the Santa-laden shop windows.

I touched his arm. ‘You all right?’

‘I don’t . . . shit.’ A tear found its way down one cheek and he smoothed it away with the sleeve of his jacket. ‘C’mere.’

In a narrow alleyway between two shop doorways, I took the paper he handed me. ‘What is it?’

He shook his head, closed his eyes and breathed deeply. ‘Read it.’

It was a photocopy. Carefully neat, with very faint lines ruled across the page.

To my son, I don’t even know what they called you but in my head you were always David.

I don’t expect you to understand anything about my reasons for trying to find you. I don’t even think I have the right to tell you what those reasons are, but I know that if you’re reading this letter, I have at least got this close to you and that means more to me than I can ever say.

I love you. I never stopped loving you, and I think about you every day. Please, if it is possible for you to forgive me to any extent, let me see you. Once, that’s all I ask. I realise that distance may make this impossible but even a photograph would help.

My darling David, you are ever in my thoughts.