‘Did Melissa tell you all of this?’ Fleet asked Zack. ‘Is that how you found out?’

‘She didn’t need to tell me. When she first turned up at the shelter six months ago, she didn’t even know who I was. But I recognised her. So I … I listened in when she was talking to the counsellor. The sessions take place in the room right next door to my office. At first it was just curiosity,’ Zack added almost defensively, as though eavesdropping were the crime he was most ashamed of. ‘I wanted to know what had happened to her. How, from being Little Miss Perfect, her life had gone so wrong. She didn’t tell the counsellor everything. She couldn’t have, because she didn’t know how Ben’s story ended.’ He turned back to Richardson, and raised the tip of the knife level with his eye. ‘But I did. I knew exactly what happened to Ben – and thanks to Melissa I found out the reasons why.’

‘And so you killed her,’ said Fleet. ‘Lance Wheeler, too.’

Zack rounded on Fleet. ‘They deserved it! And anyway, they had their chances! I knew Callum was the one behind it, and I wanted them both to help me prove it. But Melissa was a drug addict. Even if she’d agreed to help me, nobody would have believed a word she said. And in the end Lance was no more use to me than she was. When I approached him, he threatened to tell on me!’

‘So you fought. And you made his death look like suicide to buy yourself time. Time enough to get to Richardson.’

‘I could have got to him whenever I wanted!’ Zack retorted. ‘I broke into his house, didn’t I? And I proved it today. But hurting him wouldn’t have been enough. I wanted him to suffer the way I’ve suffered. To feel the same terror Ben did!’ He shook his head incredulously. ‘He wanted to be prime minister. For years he’s been sitting there in front of the cameras calling other people hypocrites. And while he was living in a mansion, being driven around in limousines, my life was in pieces!’ Once again Zack shook his head, more bitterly this time. ‘I wasn’t going to let him get away with it, not after I found out the truth.’

Your turn to hide. All of a sudden the note he’d left made a twisted kind of sense.

‘And the email?’ said Fleet. ‘The tip-off that led us to Ben’s body? That was to get us sniffing around Richardson, too? To build up to something like this?’ He spread his arms to indicate the scene around them. The fire was close enough now that smoke was drifting across the platform and the air was beginning to shimmer in the heat.