‘Come back. I’ll climb it. Call me whatever names you like, I’m not okay with you taking that sort of risk.’

‘Except there’s no way I’m strong enough to pull you back when you slip. You’ll just take me down with you and that’s not how I want to go, so follow orders, Detective Inspector. I spent my childhood climbing walls like these and in worse weather.’

Dangling from the waist forwards, Ava leaned as far over the edge as Callanach would allow her. He guessed they were around fifteen metres up and even if his estimate was wrong, given the dark and precipitation, he was certain it was a sufficient distance to be lethal. Ava cursed every few seconds, shifting along the wall, moving the flashlight to and fro, up and down, until finally she shouted out.

‘Camera!’ Ava yelled, waving the flashlight towards Callanach’s face.

‘I need a free hand. You’ll have to come back up a second.’

‘No can do. I’ll never find this again. My camera’s in the left-hand pocket of my coat. Just grab it and pass it to me.’

‘God, you stubborn, stupid …’

‘I can hear you, you know. Take the torch.’

Callanach took it, keeping a grip of Ava with his right hand as he delved into her pocket and passed her digital camera to her.

‘What is it?’ he shouted.

‘Flap of skin, I think. There’s a thin line of it snagged on the rock.’

The flash went off several times and Luc braced himself to counterbalance Ava’s increasingly outward-leaning weight.

‘Take the camera and pass me an evidence bag.’

Callanach slipped the camera into his coat and reached into his trouser pocket for a plastic bag.

‘Ava, we have to come back and do this in the morning.’

‘It’ll be gone by then. There must have been blood here given the amount of skin but I can’t see any trace of it. If Ailsa’s right about the boot mark, this might be our last chance to get the evidence.’

Callanach handed her the bag. ‘Just give me a bit more room to manoeuvre, I think there’s something else stuck in the rock.’

She shifted her weight in order to move her head downwards. The gust that took her came from the opposite direction than the predominant gale, rendering Callanach’s balance useless and thrusting him forwards into Ava’s body. She screamed, grabbed the rock face, rolling to one side and losing her grip, her right leg flying into the air then crashing back down into the jagged brickwork. Her jeans ripped from knee to ankle and her cheekbone smashed hard against the bricks.