Her eyes had now adjusted to the gloom sufficiently to see a trail of spattered but dried fluid leading up the staircase; or down it, depending on your perspective. It was still too dim to determine a colour, but Lucy had no doubt what she was looking at.

The time for creeping around in here was over.

‘Is anyone on these premises?’ she called up. ‘I’m a police officer and I have reason to believe that a crime was committed here which hasn’t yet been reported.’

Predictably, there was no response.

Despite the potential riskiness of the situation, Lucy warily ascended.

‘I said I’m a police officer!’ she called. ‘I’m here to see Roy Shankhill.’

Still nothing.

Lucy was now high enough to see a blank wall at the top of the stairs. When she got up there, she glanced left first, but saw only dripping darkness. When she looked right, it was a similar scene to downstairs: bare boards, peeling walls, but at the far end of the passage, a door stood half-open on a room so filled with stark light that she wondered if a bulb was switched on.

She traipsed towards it, treading as lightly as possible. That made no sense with her having already announced herself, but everything about this place felt wrong. Whatever the creak was she’d heard downstairs, she’d heard nothing similar up here, either on this level or from the one above – but the silence that had replaced it was a brooding silence, a listening silence.

As she approached the door, she was tempted to reach for her mobile phone, but painful experience had taught Lucy that if someone was about to attack you, it was best to have both hands free.

She pushed the door open – to the accompaniment of no sound from within, and poked her head around the jamb.

Evidently, this had once been an office of sorts. It contained a desk and a chair, and on the floor against the wall, a free-standing electric fire and a small safe sitting open but empty. There was a large window, which was too grubby to see through properly, though it admitted enough daylight to create the impression, at least compared to the rest of the interior, that an electric light had been switched on.

It served another purpose too; it clearly showed the spent shell casings scattering the floor, as well as multiple reddish-brown stains, which even though dried, still had a clotty texture. Lucy looked further, and saw erratic patterns of damage to the walls, the plaster smashed and hanging on strips of bloodstained paper, the exposed brickwork below peppered with circular holes. Bullet holes, clearly, and by their abundance, not to mention the chaotic spread, bullets fired from automatic weapons.