‘Ma’am, quick update. The blood we found inside Gilroy Western’s engine where the brakes had been cut. We’re still working up a full DNA profile, but we’ve had confirmation from the lab that it’s from a woman.’

‘Gilroy Western’s escort?’ Ava asked.

‘Lively’s traced her through the number we found on Mr Western’s phone. He’s bringing her in as a person of interest now. We’ll ask her for a DNA sample to exclude her from enquiries.’

‘Well done,’ Ava said. ‘Update me tonight? I’m expecting to be out on an operation all afternoon, but I’ll text you when I’m free.’

Back in her office, Ava let herself fall into her chair. It occurred to her that she could let Callanach know straight away that the perpetrator might be Gilroy Western’s well-paid euphemistically termed ‘girlfriend’, but decided it would be better to wait until she had more definite news. Between them, Graham and Lively would get a sense for whether or not the woman had anything to do with it. She could call Callanach later. And if that was an excuse to delay a task she wasn’t feeling up to, then who could blame her?

Chapter Twenty-Seven

15 March

Janet Monroe stood on the top of what locals had affectionately dubbed Terror Tower several years earlier, when Muirhouse was the go-to area for scoring drugs, selecting your weapon of choice, or slipping a dubious man a bundle of tens to beat up the bastard your girl was seeing behind your back. Monroe had taken a hammer and broken the locks that would otherwise have prevented her from accessing the roof, making sure she was wearing trainers she could stand in for a lengthy period before her feet were screaming at her. She was careful to make herself seen from the ground without risking a tumble in the wind.

Nothing else was faked. The police were not to attend, at least not publicly, until a bona fide concerned member of the public made the call. After that, paramedics would be made aware and suicide prevention services would be brought in. By the time the first police car pulled up, a small crowd had gathered and was staring up at the building.

Ava and Tripp were in a parallel residence, looking out over the growing crowd, checking that the cameras stationed at six different points wouldn’t miss a single onlooker. Plainclothes officers were to join the crowd at timed intervals, all wearing wires and recording conversations. Monroe herself had a more discreet transmission unit sewn into a hoodie under her coat.

‘She must be freezing,’ Ava muttered. ‘I can’t believe the super signed off on this.’