Swallow knew Caviston. A senior man. Reliable. He silently acknowledged Mossop’s logic.

‘I interviewed them separately,’ Mossop continued. ‘Two young fellas from Yorkshire. They tell the same story: drinking late in the town, they decided to try to slip back to barracks over the back wall. It’s just fifty yards across the field from the end of Blackberry Lane. But I’ve had them jugged in separate cells by their CO in the barracks. Drunkenness, indiscipline, absent without leave. He can hold them as long as we need.’

‘Did they see anyone in the lane?’

‘It was so damned foggy they could hardly see each other. They say they heard the girl scream two or three times, and they say they heard someone running. But they saw nothing. Like I said, one of them literally stumbled over the poor girl.’

‘Who got her to hospital?’

‘Caviston sent one of the young lads to hail a cab at Portobello,’ Mossop resumed. ‘They had no idea who she was until two in the morning, when a young brother turned up at Rathmines Station to say his sister hadn’t come home. They sent him down to Baggot Street and he identified her to Jack Caviston. The mother came down too. We’ve got a couple of G-men there with her.’

‘And Caviston?’

‘He finished his shift at six.’

Swallow knew that with Pat Mossop he didn’t have to ask the next question, but he asked it anyway.

‘The scene’s preserved?’

‘Laneway’s closed off. They put up a barrier with two bobbies. It was too dark for a full search of the ground. The station sergeant at Rathmines says he’ll turn out half a dozen men when we want to start.’

In the day room below, Swallow could hear voices and movement as the day shift assembled. The Lower Castle Yard below the windows was filling with a thin morning light.

‘Good work,’ he nodded. ‘I’ll take the conference below and get out to Blackberry Lane myself for the search. Just sit in with me and brief the shift, then go on home and get some sleep. Come back when you’re rested.’

The crime conference was short. Mossop rehearsed what was known about the attack at Blackberry Lane. The rest of the night’s business was routine. Two housebreakings in Kingstown. Some broken windows along Dorset Street. An assault on a publican in Ringsend. Details of each incident would be transmitted after the conference to all DMP stations through the ABC telegraph system. Uniformed men across the city would be on the alert for anything they might encounter that could be related to any of the reported incidents.