He looked at Mullen. The man had less grey in his hair than Thorne himself did, and, though the circumstances had clearly taken their toll, the rest of him looked in pretty good shape, too. ‘Well, either you’re a lot older than you look or you retired early,’ he said.

Mullen seemed taken aback for a second, but his tone was friendly enough as he led the three of them into a gloomy hallway. ‘Can’t you be both?’

‘It’s certainly what I’m aiming for,’ Porter said, hanging up her coat.

‘You’re right, though. I did bow out early,’ Mullen said. He looked Thorne up and down. ‘What are you? Forty-seven, forty-eight?’

Thorne tried not to react. ‘I’m forty-five in a few months.’

‘Right, well, I’ll be fifty this year, and I know I’d look a damn sight older than that if I’d stayed in the job. You know what it’s like. I was starting to forget what Maggie and the kids looked like.’

Thorne nodded. There hadn’t been anyone to forget for a fair few years, but he understood what Mullen meant well enough.

‘I’d managed to squirrel a bit away, and it seemed as good a time as any. I fancied a move and Maggie was pretty keen for me to get out. She even got used to having me under her feet after a while.’

On cue, Maggie Mullen came down the stairs, with every one of the fifty-odd years Thorne guessed were behind her, showing on her face. The lines had become cracks. The freshly applied make-up had done precious little for eyes that were puffy and red-rimmed. ‘I was catching up on some sleep,’ she said.

It was Holland who prevented the pause becoming a silence. He nodded towards Mullen, picking up the thread of the previous exchange. ‘It’s what politicians always say, isn’t it?’

Mullen looked at him. ‘Sorry?’

‘Whenever they leave the job, for whatever reason, they say they want to spend more time with their family.’

They stood around a little awkwardly, almost as though they were not the parents of a kidnapped child and those entrusted with finding him; as though they were waiting politely for someone to announce that dinner was served.

Now, in the living room, something of that odd formality lingered, not helped by the seating arrangements. It was a large room and the sofas and chairs had been positioned around a rectangular, Chinese-style rug. Thorne and Porter sat on a cream leather sofa with Mullen and his wife fifteen or more feet away on uncomfortable-looking armchairs, which were themselves a fair distance from each other. There was music playing somewhere upstairs, and noise too from the kitchen, where Holland and DC Kenny Parsons – the on-duty family liaison officer – had gone to make coffee.

Thorne looked out of the French windows at the garden. It was enormous compared with the postage-stamp-sized plots that graced most London properties. He turned back to Mrs Mullen. ‘I can see why you moved here. I wouldn’t fancy mowing it, mind you.’

It was Tony Mullen that responded. ‘This place was a compromise, really. I was all for upping sticks completely and getting out into the country, but Maggie didn’t really want to leave London. It feels like you’re in the country here, but you’ve got High Barnet tube a few minutes away, or you’re twenty minutes from King’s Cross on the overground.’

Thorne made the right noises, thinking: This is a world away from King’s Cross.

‘And the schools,’ Maggie Mullen said. ‘We moved because of the schools.’

Then, with that one meaningful word, the terrible reason for them all being there was finally in the room with them, and the small talk was well and truly done with.

Tony Mullen slapped his palms against his legs, the noise causing his wife to start slightly. ‘We know it’s not bad news, thank God, but I presume that there isn’t any good news, either.’

Porter edged forward on the sofa. ‘We’re doing everything we can, but-’

‘Don’t.’ Mullen raised a hand. ‘I’m really not interested in the pat speeches. I know the game, remember. So let’s not waste anyone’s time, all right, Louise?’

Thorne could see that Porter was more than a little irked at the familiarity, but he thought she was probably not the type to react. Not the first time, anyway. Instead, she let her eyes drift across to Mullen’s wife and spoke softly to her. ‘It wasn’t a speech.’

‘I’m the new boy,’ Thorne said, ‘so you’ll have to forgive me if we go over some old ground, but I was wondering about the delay.’

Mullen stared right back at him. It was a grudging invitation for Thorne to elaborate.

‘Luke went missing on Friday after school, but the first call to the police was made at a little after nine yesterday morning. Why the wait?’

‘We’ve already explained all this,’ Mullen said. The edge to his voice revealed traces of a Midlands accent. Thorne remembered Porter telling him that Mullen was originally from Wolverhampton. ‘We just thought Luke was out and about somewhere.’

‘Only on Friday evening, surely?’

‘He could have gone to a club, then stayed over at a mate’s or something. There was usually a certain amount of leeway on a Friday night.’

‘It was me.’ Maggie Mullen cleared her throat. ‘I was the one who thought there was nothing to worry about. I was the one who persuaded Tony that we should just wait for Luke to come home.’

‘Why didn’t you say this yesterday?’ Porter asked.

‘Is it really important?’ she said.

‘I’m sure it isn’t, but-’

‘We waited. That’s all that matters. We waited when we shouldn’t have and I’ll have to live with that.’

‘There was an argument,’ Mullen said.

Thorne’s eyes stayed on Maggie Mullen. He watched her drop her head and stare at her feet.

Mullen sat up straight in his chair and continued. ‘Luke and I had a stupid row that morning. There was a lot of shouting and swearing, the usual kind of stuff.’

‘What did you argue about?’ Thorne asked.

‘School,’ Mullen said. ‘I think maybe we were putting him under a bit of pressure. I was putting him under pressure.’

‘Luke and his dad usually get on so well.’ Maggie Mullen looked at Porter, spoke as though her husband were no longer in the room. ‘Really well. It’s not normal for them to argue like that.’

Porter smiled. ‘The fights I used to have with my mum and dad…’

‘Sometimes I think Luke’s closer to his dad than he is to me, you know?’

‘Don’t be silly,’ Mullen said.

‘I get jealous sometimes, if I’m honest.’

‘Come on, love…’

Maggie Mullen was staring straight ahead.

Thorne followed her gaze to the elaborate fireplace; to the flame-effect gas fire and the half-life-sized ceramic cheetah sitting to one side of it. ‘Was this row really that serious?’ he asked. ‘Serious enough for Luke to leave without a word?’

‘No way.’ Mullen was categorical. Said it again to ensure that Thorne and Porter got the message.

‘Mrs Mullen?’

The drum and bass coming through the ceiling seemed louder for a few seconds. Still staring towards the fireplace, Maggie Mullen shook her head.

‘Whether it’s got anything to do with this argument or not, Luke’s disappearance may still have a simple explanation.’ Porter waited until all faces were turned to her before carrying on. ‘We’ve at least got to accept that possibility.’

Maggie Mullen stood up and smoothed down the back of her skirt. ‘I’m happy to accept it, love. I’m praying for it.’ She walked across to the fireplace, reached for a packet of Silk Cut on the mantelpiece.

‘Obviously, we’ve checked out all his friends,’ Porter said. ‘But in the absence of any sort of communication from anyone who might be holding Luke, there has to be a possibility that he’s gone away with someone.’

‘You mean this woman?’ Mullen said.

‘He’d been spotted with “this woman” on other occasions.’ Thorne stood up too and walked behind the sofa, the relief from the pain in his leg almost instantaneous. ‘If Luke’s seeing an older woman, he might have thought better about telling you.’