The picture Harry had seen online was two years old, and puberty had kicked in since. Charlie had let her hair grow, framing a face still dominated by huge blue eyes. She was around average height for thirteen, built on a broad frame, and she’d sweated in the heat so that her black bra showed through her pale blue T-shirt. Her chunky legs had a line of scabs from a fall and she had the tough, blackened soles of someone who liked going barefoot.

‘So, you’re a photographer,’ Charlie said as she found the replay button on the camera and flipped through his pictures.

Harry eyed the gun. He was a good runner, but it still wasn’t far enough from Charlie’s reach to try to escape.

‘Is this where you’re from?’ Charlie asked, turning the camera round so that Harry could see a view of a sunset over a cityscape.

‘You’ve gone past the end to the first pics on that memory card,’ Harry explained, trying to tame the fear in his voice. ‘I got the camera for Christmas, and took it on a Boxing Day walk with my dad. It’s the view over London from the top of Hampstead Heath.’

‘Nikon,’ Charlie said, inspecting the lens. ‘Must have cost plenty.’

Harry nodded. ‘It was my main Christmas present two years ago, and I saved money to buy extra lenses and stuff.’

‘What’s your name?’

‘Harry.’

‘Smirnov?’ Charlie replied sharply. ‘You made the video of Deion.’

‘Yeah,’ Harry admitted, stifling a cough with more of the tepid water. ‘That footage is on my phone.’

‘Did you follow the cops here?’

Harry shook his head. ‘I asked around. People said you made some explosives …’

‘It’s not hard,’ Charlie said, nodding. ‘Swiped most ingredients from CVS next door, and found the rest online.’

‘Mixing explosives sounds dangerous,’ Harry said, intrigued that Charlie seemed keen to talk.

‘The trick is to practise with tiny batches. The guys who get their hands blown off are the ones that throw sacks of chemicals in bathtubs before doing proper tests.’

Harry laughed, at least as much as you can laugh when your throat is scratchy and the person you’re talking to is two feet from a gun.

‘But it’s been more than two years since I mixed a batch.’

‘Why’d you stop?’

‘All kids have their phases,’ Charlie said dismissively. ‘Some get obsessed with guns or knives. Boys light trash on fire, or torture frogs. I was the science geek who blew stuff up.’

Charlie seemed embarrassed, making a little snort and looking down at her grubby feet. The way she was opening up made Harry think he might be on to another story, and gave him hope that the cops wouldn’t be finding his bullet-riddled corpse.