Beth followed O’Dowd along the footpads laid by the CSI team as they made their way to the cellar. Either side of them, knee-high nettles brushed against their trousers looking for bare flesh to sting.

The nettles dwindled as they made their way into the house, which, despite its name, Beth couldn’t think of as a castle without an encircling wall complete with crenelated battlements. In a far corner there was a tree stump whose top showed bright yellow, indicating the recent attentions of a chainsaw. Large areas of the floor were covered with debris that had fallen from the wall tops and every one of the walls featured the pink sandstone used to construct the house. Regular holes cut into the walls marked where floor joists had been positioned and there were empty blackened pockets which had once been fireplaces.

Unlike Arthuret Hall, Highstead Castle didn’t carry so much as a hint of eeriness. It was tranquil, benign and seemingly innocent. But while the house couldn’t assume guilt, there was no question that someone was responsible for the bodies that lay in its cellar.

The footpads led to a doorway in a wall where a staircase stretched down to blackness and then stopped. O’Dowd’s torch flashed across the rubble and weed-strewn steps. ‘Bloody cowards. When we leave here, remind me to let that bunch of CSI chickens know a pair of girls had more guts than them.’

Beth didn’t answer. Instead she pointed her torch at the stairs and picked her way down carefully after the DI. Cobwebs lined the corners between wall and ceiling, and there were large patches where the plaster of the cellar’s ceiling had fallen away to expose the timber laths. There was scurrying as rodents retreated from the invasion of their domain. The air contained mould and decay and hung with a stench that was dark and malevolent.

As Beth reached the wall that ran to her right at the bottom of the stairs, she realised that despite the fact she was breathing only through her mouth, the smell was pushing insistently up her nose. In the absence of VapoRub, she pulled a packet of mints from her pocket and stuffed one up each nostril.

O’Dowd’s torch began a slow anticlockwise sweep of the cellar. When it got to ten o’clock it picked out a body. A naked man.

Further round it swept, nine, eight o’clock, more than once it picked out a pair of eyes or a long tail, and then at seven, it picked out another naked form. This time it was a woman.

Together the two police officers stood at the foot of the stairs – O’Dowd had insisted they go no further so as to minimise their contamination of evidence – and shone their torches over the woman’s body.

What Beth saw would live with her forever. The lower parts of the woman’s legs were eaten away to the point of being skeletal, her arms hung from the ties binding her to the wall and while they couldn’t see her face to judge her age there was a firmness to her form that suggested youth.

When their torches played over her back, Beth’s gasp beat O’Dowd’s by the merest fraction of a second. A pair of colourful wings were fixed there. To Beth they looked to have belonged to a parrot or some other exotic bird. Like the ones on Angus Keane’s back, the wings were folded neatly against the body. There were areas on the woman’s shoulders and neck which showed where rodents had climbed up and, having found a perch, gorged upon her bare flesh.

Something at the edge of the torch’s beam caught Beth’s eye and made her redirect her aim.

‘Ma’am, do you see what I see?’

‘If you mean the scorched effect on the laths by her head, then yes, I see it. Let’s have a look at the guy now.’

Beth’s torch found him first. He was tied to hooks, which she guessed once held cuts of meat or game birds. His arms were spread wide and there was not a stitch of clothing on him apart from laceless boots on his feet.

It wasn’t the most striking thing about him though. That was the pink flesh which remained unsullied by decay. A number of bite marks covered his body, but unlike the woman in the opposite corner, at no point could Beth see bone.

Her torch crept up his body, past his genitals and over his taut stomach and hairy chest until it showed his face. His mouth was a blackened pit, with burn-blistered lips that had contracted back to expose every tooth in his mouth.

O’Dowd’s torch then traced the outline of his body and, just as Beth expected, the tip of a wing protruded from his back. This wing bore no vibrant colours, instead it was made up of speckled brown shades designed to camouflage its owner rather than attract a mate.

Holding her torch away from her body, Beth gave the cellar another scan. As much as she wanted to leave and breathe fresh air again, there was something nagging at the back of her mind and she knew it was connected with a detail she’d just seen in the cellar.

The foot of the walls gave her no clue, so she lifted her torch and traced round the edge of the ceiling. Nothing. She zig-zagged the beam across the floor and still found nothing. Exasperated, she eased the torch around the room at waist height. When the beam returned to its original twelve o’clock position, she found what she was looking for.

There was a door handle protruding from the wall on their right.