It was almost noon before I realised that I hadn’t eaten my yoghurt, warm now, but I ate it anyway. Then I rang Tina and asked her to bring up coffee for both of us. I had already forwarded her my updated notes for saving to the office case management system. I guessed that Tina would have read them and that she would have an opinion on Joey O’Connor.

‘The way I see it, Finn,’ Tina said. ‘Either Jeremy Gill did it or we have nothing. The only reason we’re doing this loopy case is because the dad thinks it’s Jeremy. He never mentioned Joey to you. Never asked you to go near him. Now, have a Jaffa Cake, it’s the best brain food there is.’

I took the biscuit and ate it in two bites. Tina had a point. I had to bear Joey in mind, and any other signs of Gill’s possible innocence. But surely I wasn’t obliged to give equal weight to every lead? Sean had come to me with his concerns about Gill, and Gill alone.

‘I wish I’d had you to talk to at four o’clock this morning,’ I said. ‘I was tossing and turning half the night trying to sort it out in my head. Though if you’d met Joey …’

‘I don’t have to meet him,’ Tina said. ‘He sounds like a complete langer altogether.’ I couldn’t have put it better myself.

I was waiting by the bike stand on Emmett Place when Marie Wade emerged at three minutes past one. I had called her at work at the Opera House accounts department. She had agreed to meet me at lunchtime: she took a stroll every day and had said I was welcome to tag along.

‘Now I remember,’ Marie said. ‘I couldn’t put a face to the name on the phone earlier. You all set to go?’

‘Ready when you are.’

The North Face waterproof jacket and serious walking shoes should have been a portent. She took off at speed over the Christy Ring Bridge, but it was only when we got to the top of Coburg Street that the full horror of her lunchtime regimen became apparent: repeated trips up and down Patrick’s Hill, Cork’s meanest slope. Though the view made it a worthwhile slog any time, that wasn’t why Marie did it.

‘I’m going skiing in January,’ she said. ‘I go every year. This is great for the muscles.’

At the top, with the green of Bell’s Field dipping towards Blackpool, and the houses heaped to the summit of the hill opposite, and Cork’s shabby magnificence laid out before us, she paused long enough to examine the photo of Daniel O’Brien I had saved to my phone.

‘I remember him,’ Marie said, as she started the descent. ‘Nice guy.’

‘So I hear,’ I said. ‘Any word from him after he left?’