‘I do, for all the reasons you just stated. I can’t give you anything to go on scientifically speaking yet, but the simplest explanation is usually correct. You have a serial killer in the area who’s ramping up. Truth be told, we were all waiting for the next victim. Until we have DNA, prints or reliable witnesses you can’t be certain, but this is a level of violence and degradation that few people are capable of. I seriously hope, for all our sakes, that it’s just one killer. The thought of having two such psychotic individuals active at the same time in this city is unbearable.’

Ava rang off and went to find DS Tripp. She located him in a new-looking barn a couple of fields away, where officers were hastily erecting floodlights and removing articles in evidence bags.

Taking the ladder to the upper area of the barn, Ava went to see what all the fuss was about. A couple of bin bags filled with food wrappers and general debris had been cut open for inspection and four large water canisters were stacked in a corner, mostly empty. A few tatty blankets had been left, together with shoes that were more holes than leather, and clothes certainly not designed for Scottish weather.

‘Several people living here for some time, we reckon,’ Tripp said, appearing behind her.

‘The farmer must have known. Most likely they were getting shelter in return for cheap labour,’ Ava said.

‘So it’s either the homeless, kids or people who’ve fallen on hard times, maybe criminals with nowhere to go and no other offers of work …’

‘Or illegal immigrants,’ she finished for him. ‘We’ll need DNA from all the items to identify the people who were here. There’s no dust settled on any of this, and no spider’s webs either, so it looks like they left recently and in a hurry.’

‘Do you suppose one of them’s responsible, ma’am?’ Tripp asked.

‘Anything’s possible, Sergeant. What I need to establish right now is a motive. The body’s been removed to the mortuary. Thought you might want to do a walk-through of the rest of the property with me.’

They retraced their steps back to the house, avoiding the units checking every inch of the dirt track for fresh tyre prints.

Ava tried the front door. It was locked and bolted from the inside. All downstairs windows were intact and also locked.

‘So the killer came in through the back door, but there’s no evidence of force being used. Either the victim let him in, or he just walked straight in when it was unlocked,’ Tripp said. ‘No gun in the cabinet, so we’re assuming the one that was found on the floor next to the body belonged to the farmer.’ Tripp’s phone rang. ‘Excuse me, I should take this,’ he said, moving into the lounge.