‘Maybe your man felt like going out for a late push after work,’ suggested Detective Sergeant Begley. Then shrugged and said, ‘Only a thought, like.’

Katie pointed to Dr Power’s sketch map. ‘If he is employed, then his place of employment can’t be too far away from the city centre, although there’s a distinct bias to locations off to the east… Horgan’s Quay and the Port of Cork Garden and Tivoli Pier and of course The Marina.’

Dr Power said, ‘Now this is only supposition, but let’s say that there’s a strong possibility that the Pusher is in employment. He probably doesn’t hold a highly paid position because a man in a highly paid position would be less likely to harbour chronic feelings of resentment, and he’d also be more likely to have time off whenever he wanted it. What’s more – if the Pusher has only a limited time frame in which to go out looking for people to drown, I doubt if changing his clothes is a high priority. His grey tracksuit could well be what he wears all day, at work. He may actually keep it on deliberately as a symbol of the oppressed person that he believes himself to be.

‘As I said before, many or most mass murderers want to teach the world a lesson of one sort or another. Quite often that lesson is connected to their own job or their own interest in life. I had a Bus Éireann driver in Drogheda once who was sacked after a disabled passenger complained that he wouldn’t let her on to his bus, and so the next thing he did was drive his car into a crowded bus stop. He killed three people and seriously injured seven. By that token, I think you could make a reasonable start by checking all the sports teachers and football coaches in Cork, and in particular any swimming instructors.’

Katie looked over at Detective Inspector Mulliken and Detective Sergeant Begley. ‘Do we know any schools whose gym teachers wear grey? How about the Ursuline Secondary School in Blackrock? Or GAA club coaches? Or leisure centre instructors? We have the three public swimming pools, don’t we, at Bishopstown and Churchfield and Douglas, and then there’s the hotel swimming pools, too, like the Clayton and the Maldron and the Montenotte.’

‘I don’t think that Cork is what you might call overpopulated with sports coaches and swimming instructors,’ said Detective Sergeant Begley. ‘I’ll have Caffrey and O’Crean go round the schools and the pools and the GAA clubs and track down as many as they can.’