Tom recognised Mark Dunne, the man Emmet had summoned with his roar. He had worked with the Tech Bureau for a few years and was a friendly chap, good at his job. He was a big rugby player in his spare time, from what the inspector recalled, and had the cauliflower ears and misshapen nose to prove it.

‘Tom, you know Mark, don’t you? Right, well, as it turns out, my assistant is a bit of a nature expert.’

‘Ok-ay.’ Tom drew out the word, one eyebrow raised quizzically. ‘What’s the relevance?’

‘Do you know much about Glendalough?’ Mark asked.

‘Tourist facts.’

‘Okay, so, before I went into forensic science, I studied botany. I’m familiar in particular with the flora and fauna of the Wicklow Mountains National Park.’

Tom and Ray stared at him blankly.

‘Eh, let me give you some context. You see these trees around us? They’re mainly oak trees. Centuries ago, the trees in Glendalough were coppiced – cut down and regrown from their stumps. It was good practice for managing woodland, but they overdid it here and lost a lot of the trees. Around the mid-eighteenth century they replanted but there are still little glades like this one here and there, a legacy of the coppicing. In the main, though, Glendalough is filled with deciduous woodland – that means the trees are so thick overhead that there’s competition for light and space to grow. So the plant life in these woods has adapted. It has stratified.’

‘Go on,’ said Tom, still at a loss as to where this was heading.

‘Well, you’ve the trees at the top – the canopy layer. Then there’s the shrub layer, holly mainly. There’s a ground layer of mosses. The grass-height plants are called the herb layer. These have to be clever to survive in such a fierce environment. You still with me?’

‘So far, and kudos for your extensive knowledge of Glendalough greenery,’ the inspector replied, wryly. ‘What’s the point, though?’

Mark produced an evidence bag and withdrew from it a delicate blue flower. Soil still clung to its roots.

‘This, in layman’s terms, is blue-eyed grass. I found it amid the loose soil covering the victim. It was a genius choice. Whoever planted it here knew their flora. Blue-eyed grass will thrive in damp soil and we’re near a lake, but this plant is native to marshes and wetlands in the west of Ireland. Not here in the east and not in Glendalough.’

‘So, somebody brought it here and placed it on the grave?’

‘No. As I said, it was planted,’ Mark replied.

‘But you said …’

‘Look at the ground around us, Tom,’ Emmet interrupted.

The inspector frowned and examined the earth under the trees. As he scanned the glade, his stomach lurched.

One, two, three, four. Five, counting the mound of earth disturbed under the tent.