‘When somebody you love dies, you think, Holy Mary, we’re all going to die anyway, so what’s the use of worrying about it? All this stuff about exercise and cutting down your drinking and not eating meat. Those three poor souls we have lying in the morgue there right now, they could have been swimming forty lengths a day and eating broccoli until it came out their ears. None of it kept them living any longer, did it?’

Katie took hold of her hand. ‘I’m so sorry about your father, Mary. I think I met him once. He used to be head of cardiology at the Mercy, didn’t he?’

‘That’s right. And he died of a myocardial infarction, would you believe, on his seventy-eighth birthday. How ironic is that? One minute he was sitting at the piano singing “The Rising of the Moon”. The very next minute he was taken away from us.’

Dr Kelley led Katie into the morgue.

‘Roisin Carroll’s parents rang me to say that they were running late, but they should be here by 4.30. It’ll give us some time to have a good look at Justice Quinn, anyway, and Billy Hagerty.’

‘You said there was something interesting about Billy Hagerty.’

‘I did, yes, and that was probably the understatement of the century.’

The morgue was as chilly as ever, with washed-out rays of sunlight falling from its clerestory windows, like fine net curtains. Despite the fierce air conditioning and the tang of antiseptic, there was still a faintly rotten odour of dead bodies.

‘That’s Justice Quinn over there,’ said Dr Kelley, pointing to a trolley by the opposite wall with a pale green sheet draped over it. ‘And here’s your man.’

Billy Hagerty was still lying on the stainless-steel autopsy table – although he, too, was covered by a pale green sheet, stained on one side by a moth-like pattern of dried blood, which resembled a Rorschach test.

‘We’ve wheeled Roisin Carroll off to the visitors’ observation room, ready for her parents to see her. I combed her hair myself, the young angel. She looks like she’s fast asleep, not passed away.’

‘It was tragic, her being drowned like that,’ said Katie. ‘Absolutely pointless, too. We have a psychologist coming down from Trinity College later today to see if we can come up with any reason why this header might be pushing people at random into the river.’

‘Pity your man here’s dead. Now he could have had a few interesting things to talk to your psychologist about, and no mistake. Denis!’

Dr Kelley’s skinny young assistant came in from the sluice room at the back of the morgue, his white lab coat hanging around him as if he had just landed by parachute.

‘Would you—?’ Dr Kelley asked him, gesturing that he should lift the sheet off Billy Hagerty’s body. Denis dragged it off and clumsily folded it up.