They emerged through a doorway into dazzling sunlight. Small trees and shrubs in large stone tubs had been arranged in what Patrick thought of as a kind of Japanese-style garden, with neat beds of grey pebbles in a square pattern that stretched across most of the rooftop. Beyond: London. The great, grey city. St Paul’s looked like he could reach out and scoop it up. He could see all the way to Essex, but he couldn’t immediately see Penny and Frankie.

A man wearing the by-now familiar hotel uniform of white shirt and navy jacket, his name badge informing them he was called Kurt, hurried up to them.

‘Police? Oh thank God.’ He looked over Patrick’s shoulder. ‘Er, where are the rest of you?’

‘On their way. Where is she?’

Kurt pointed towards the far corner, which was obscured by trees and a couple of large parasols. ‘Over there. She’s got a little girl with her. And a gun.’

Patrick took a deep breath. ‘Is this the only exit, Kurt?’

‘No. There’s the main entrance-exit over there. But we’re guarding it.’

‘Okay. But, listen, if she comes out, you all just get out of the way. I don’t want anyone trying to be a hero, OK?’

Kurt put his hands up. ‘Hey, don’t worry about that. Not on our wages.’

Patrick and Carmella walked slowly past the garden, the sun beating down on them. As they neared the edge of the rooftop, the woman they had been seeking for what felt like a lifetime came into view.

Penny Philips – or Marion Ellis as she called herself now, as he had learned from her Facebook exchanges with Helen – was standing in the corner, her back against a low wall. Frankie Philips was lying, curled up, at her feet. He knew small children had the ability to go to sleep in the most unusual circumstances, but Frankie had to be drugged. If she was alive.

Penny, who had been staring at the concrete in front of Frankie, noticed them, her head snapping up. She lifted the gun and pointed it first at Patrick, then back at Carmella, then at Patrick again.

‘Keep back,’ she said. ‘Don’t come a step closer.’ She had an accent, a hint of Australian mixed with Estuary English.

Patrick spoke soothingly. ‘Penny . . . is it alright to call you that?’

Surprise briefly registered on her face, before she affected confusion. ‘My name is Marion.’

‘No. It’s Penny. But we can call you Marion if you wish. And I know you haven’t hurt any . . .’ He was about to say anyone but remembered Jerome downstairs with his head missing. ‘. . . any children. How is Frankie? Is she OK?’ He took a step closer. His heart felt like it was trying to escape his chest.

Penny jerked the gun at him. ‘I said, don’t come closer.’