‘Hmm. Now there’s a question. It’s more likely that the Munster region is his hunting ground and he buries them close to where he lives so he can keep an eye on them, visit them, that sort of thing. So you’re looking at Dublin and its surrounding counties for his home – Wicklow, Kildare. I’d pay special attention to Meath, where Fiona lived. It would fit with the escalation theory that he would take somebody from near his home, possibly somebody he’s known for a long time. He might be a man who travels a lot and especially to the south – a sales rep, something like that. Most serial killers are occupationally mobile. It’s entirely in keeping with the facts that he would kidnap and kill in one place and dispose of his victims in another.’

She turned and wrote: Geographically mobile.

‘Why does he do it?’ This was Ray. He’d crossed over to where Tom was sitting and reclaimed his half-empty bottle of water, throwing his boss a dirty look.

‘I can give you all the clichés, and unfortunately they’re usually true. It’s most likely, unless we have an extremely rare, utter psychopath on our hands, that the killer comes from an abusive background and that he was either abandoned young by a parent, or later by his wife. But none of that will be apparent in his day-to-day behaviour. What you should also be on the alert for is a groupie. Somebody who wants to be involved with the case.’

As she was writing this, she continued to speak over her shoulder.

‘You should keep an eye, too, for a direct link to one of the victims – most likely the first or second. It’s highly probable that he was consumed with the desire to kill one specific woman and he’s been trying to recreate that feeling ever since. I say first or second because he may have killed a stranger first so he could be sure he was capable of doing it.’

Tom had been listening so intently he’d completely forgotten that he’d been sweating prior to Linda standing up. In fact, his body temperature seemed to have plummeted. It didn’t help that the psychologist was describing the most horrific things in such a polite, matter-of-fact way.

‘At the scene,’ he said, wanting to squeeze every last drop of valuable knowledge from her, ‘Emmet said that the body we think is Una Dolan appeared to have been dug up and reburied, shallow enough that she was easily found by the dog. The other bodies were much deeper. What motive could the killer have had for digging her up?’

Several officers in the room turned a distinct shade of green – including Ray, despite being already aware of the grisly fact.

‘Do you remember, Tom, a couple of years ago we got into a conversation about that book your wife loves – Wuthering Heights?’