Dan was sizing up the room while Sophie was speaking but the distress in her voice must’ve pulled him up too, as he turned his attention to her.

‘Sorry to hear that,’ I said. ‘I know how difficult it can be when someone isn’t around anymore.’ Sophie wasn’t to know quite how intimately I understood this.

‘We only moved in here four months ago and now we’ve got to find somewhere else because the block is being sold for development. Mum had to buy furniture ’cause Dad needs ours for his new family . . .’ Her sentence petered out as she began to cry.

I felt sorry for Sophie and her mother, and wondered why she was telling us all this when I’d asked her about the flash mob. Either something was wrong, or she’d learnt deflection skills early in life. ‘What are you worried about? Is it your mum?’

‘She’s started drinking again.’ I detected shame in Sophie’s voice. ‘It’s why Dad left us . . . and left me to look after her. Last night she didn’t come home at all. I’ve rung her mobile but it goes straight to voicemail, and I’m starting to get scared.’

‘When did you see her last?’

‘Yesterday morning. Before I left for college.’

‘Did you speak to her in the day?’

‘No. I rang her to say I was going to Brick Lane, but she didn’t answer.’

This wasn’t what we’d come about but Sophie was still a minor and we had to refer on the fact her mother had been missing for thirty-six hours. More worryingly, it occurred to me that Sophie’s mother might be the woman in the fire. ‘Have any of her friends heard from her? Or anyone else in the family?’

‘I’ve rung everyone I can think of, including Dad. Nothing.’

‘We’ll need her full name, description, a recent photograph, work details and where she goes drinking, please. Plus her mobile number, and your dad’s contact details too. Can you do that?’

Sophie set about collecting together the information we’d requested, and it gave me the chance to check in with Dan, whose face was the mirror of mine.

‘Could be in the right age range,’ he whispered. ‘Missing since yesterday, mobile going to voicemail?’

I nodded.

Having got the information we needed, we returned to the subject of the arson attack.

‘How did you get involved with the flash mob?’ I asked her.

‘Oh yeah. Have you got my bag? It’s got loads of my uni stuff in it, and my phone.’

I explained about the forensic tests and that we’d let her have the returnable items as soon as we could. ‘We understand you’ve had some dealings with a website called LfA. Is that where you learnt about the flash mob?’