When she returned to the living room she gave DS Anderson everything she’d collected and he nodded his thanks. ‘Luke left his mobile behind too,’ she said, handing it to him. ‘The code’s 1609.’ The sixteenth of September. Her birthday. She remembered how he’d smiled and said, ‘That way I’ll never forget.’ She watched as that, too, was efficiently deposited into a clear plastic evidence bag.

Anderson turned his attention to Mac. ‘And how about you, Mac? How long have you and Luke been friends?’

‘Eighteen years. Since we were eleven.’ Clara almost smiled at the way this giant Glaswegian was suddenly sitting up straighter, his knees pressed neatly together, meek as a kid in front of his headmaster.

‘And there was nothing about his behaviour recently that struck you as unusual?’

‘No … I don’t think so, no.’

Clara glanced at him. Was there something a little strange about the way Mac said that? The brief hesitation before he spoke, something slightly off about his tone? She couldn’t quite put her finger on it.

Twenty-five minutes after they arrived, the two officers got up to leave. ‘I think I have all I need for now,’ Anderson told them. ‘I’m going to talk to Luke’s parents and his employers next.’ He paused, consulting his notes. ‘Brindle Press? W1. Is that right?’ When Clara nodded he went on, ‘We’ll also look at any relevant CCTV footage, to see if we can trace his movements after he left work yesterday.’ He glanced at Mac. ‘And if you could both think about anything that might have happened in the last few weeks that could be relevant – any unusual phone calls, anything out of character he might have said to either of you, or any change in his usual behaviour …’

‘Yes, yes of course,’ Mac and Clara said together.

He nodded. ‘We’ll be in touch.’

After they left, Clara sank on to the sofa. ‘Jesus,’ she murmured. She put her head in her hands. ‘At least they’re taking it seriously, I suppose.’ When Mac didn’t reply she turned to find him standing with his back to her, gazing out of the window. ‘Are you OK?’ she asked.

He was silent for a while, and then she heard him mutter something to himself. She stared at him in bewilderment. ‘Mac? What’s the matter? What is it?’

He turned to face her. ‘Jesus, Clara, I’m so sorry.’

‘Sorry? What on earth for?’

He raked his fingers through his hair in agitation. ‘I really didn’t want you to find out like this. But it’s all going to come out now – the police are going to talk to everyone – his work, his friends; everyone, and I don’t want you to hear about it that way.’

‘For God’s sake, Mac! Hear about what?’

Mac closed his eyes for a moment. ‘Luke’s affair.’