‘You know that’s daft. It’d be normal to feel that way after two years. Look, I’m no grief expert, but I don’t think you ought to be wondering if you’re doing anything wrong. Do whatever makes you feel better. But I mean … at the same time, don’t put pressure on yourself to feel better. A lot of misery comes from telling yourself you’re feeling the wrong way. If that makes sense.’

‘Yes, it does.’ Lisa smiled. ‘Thanks.’

‘You’re welcome. And thanks for letting me take another look at Josh’s flat. I might not see anything that I and my team didn’t see all the other times we were here, but it’s still helpful for me to be here.’

‘But you might find something new.’ Lisa’s voice rose in pitch.

Sellers decided to be honest. ‘It’s possible. I don’t think there’s much of a chance, but I’m still hoping I will, and feeling as if I might. A lot of my friends think I’m a deluded optimist. It’s stupid, but – for reasons I won’t bore you with – I care more about catching Josh’s killer than I’ve ever cared about catching any scrote before.’

‘Well, I’m all for deluded optimism,’ said Lisa. ‘For as long as I live, I’m going to believe you lot are just about to catch him.’

Sellers felt winded. What she’d just told him, without realising it, was that she expected them never to catch Billy. Corresponding with Sellers’ own fears as it did, that wasn’t an easy thing to hear.

‘It’s the only way I can live. If this were a movie, I’d say, “When you catch him, don’t arrest him – bring him to me. Let me deal with him.” God, the fantasies I have about what I’d do to him. And then I wonder if I’ve allowed a monster to turn me into a monster,’ Lisa added tearfully.

‘You’re no monster. Every single relative of a murder victim has those same revenge fantasies. The police have them too.’

She sniffed, then giggled. ‘Hey, do you fancy a cocktail? I’m no mixologist, but how hard can it be? It’s just shaking up some booze and sticking it all in a glass at the end of the day, isn’t it?’

Sellers, who’d had too much to drink the night before, couldn’t think of anything he wanted less. ‘Tell you what,’ he said. ‘You make us cocktails – though not too much of the hard stuff in mine, if that’s okay. While you’re doing that, I’ll do my walkaround of the flat.’

‘Deal,’ said Lisa. ‘Josh had a silly song he used to sing whenever he made a cocktail. He called it his magic ingredient. If he didn’t sing the song, the cocktail wouldn’t taste right.’