The door to her flat stood ajar and, as he crossed the threshold, he heard no voices from the kitchen. As he closed the door behind him, the cat appeared like a flash to accompany him.

She was seated at the kitchen table, a pizza box and glass of wine alongside her open laptop.

‘If you’re not on duty, there’s beer in the fridge. Or,’ she said, reading his expression, ‘whisky in the usual place. Plus there’s pizza left. I always order enough for two.’

She went back to studying her screen while he helped himself to a slice of pizza. Eventually she shut the laptop down.

‘I was planning on giving you a call,’ Rhona said.

‘That makes me feel better about the intrusion. Thought I might be interrupting your evening.’

‘There’s no one here but Tom and me.’

Many of their exchanges over the years had been fractious, sometimes outright furious, especially if or when they’d strayed from work and into their private lives. He wondered which of the two her proposed call had been about.

‘Bill checked in about the forensic material we had on Steven Willis,’ she said. ‘We can put him in the room, and we have evidence of him on the handle of the bag and the credit card. The semen retrieved from the victim is not a match. I understand Willis has given you a lead on the Go Wild man who rented the flat from him?’

McNab nodded. ‘That’s why the boss let us set up the sting for later tonight.’

‘So that’s not why you’re here?’ she said, meeting his eye.

He indicated it wasn’t. ‘It’s about Ava Clouston.’

‘I thought it might be.’ She fell silent for a moment, then said abruptly, ‘Why didn’t you pursue Mark’s warning about Cleverly? And don’t say it was because of what Jack Winters told you. You didn’t trust Cleverly before, and with good reason. Why would anything Winters have said change your mind?’

Stung by that interpretation of events, he came back at her. ‘It didn’t. Mark was killed because of what he unearthed, and that included what he’d found out about Cleverly.’

She nodded, as though accepting his response. ‘Ava called me shortly before your arrival,’ she said. ‘They’re both well and staying with Firash’s family at the cafe.’

Relief threatened to swamp him, revealing, even to him, how truly worried he had been.

‘Ava said that Mark’s diary indicated he was meeting with a police officer the evening he was murdered,’ she told him.

‘I know,’ he blurted out. ‘I just don’t know who.’

‘She believes it was DI Cleverly. I recorded what she said.’

McNab listened as Ava’s voice rang out, strong and determined, ending with, ‘Cleverly has a son who’s involved with Go Wild. That’s who he’s covering for.’