‘Staff take the orders on the left,’ Mango explained quietly, pointing to the line at the register. ‘Everything on the payment side is secure. One-twenty-eight-bit encryption, credit card and NFC data handled securely. But you see that other terminal, that shows the drink orders to the mixers? It links to the register using WiFi. There’s no encryption whatsoever.’

To make her point, Mango tapped a code into her phone and the screen split.

‘The top half shows the current queue of customer orders. You’re seeing exactly what the two staff mixing drinks see. Now, all I do is tap an order number and two product codes, and …’

Charlie saw an order for Almond Sunrise and Maternal Bliss appear as order seventy-three in the drinks queue.

‘Neat,’ Charlie said, wary, because trouble seemed to seek her out. ‘So you’re a hacker?’

‘I hoped I’d catch you with my bike, because you remind me of myself as a teenager,’ Mango explained. ‘You made explosives. I worked out how to clone my seventh-grade gym teacher’s cell phone and credit card. Then I went online and arranged to have all kinds of crazy stuff delivered to his house.’

Charlie smiled. ‘Did you ever get caught?’

Mango nodded. ‘Things got heavy when I was seventeen. I helped an environmental group find and release a secret Department of Energy report on fracking. I had FBI agents raiding my parent’s house at 3 a.m. We were well off. My dad fixed up a great attorney and I pled down to a misdemeanour charge. I was sentenced to two hundred hours teaching computer skills to San Francisco homeless. It was in one of the first maker spaces, and that’s how I got into teaching kids coding and engineering.’

‘Do you work in IT now?’

Mango shook her head. ‘My wife and I have a baked-goods business. We do specialist cakes and breads. And we have vans that we send out to music festivals and big public events.’

‘Sounds like hard work,’ Charlie said.

‘I’ve had a lot of fun teaching kids over the years,’ Mango said. ‘We did a battle robot course with ten- to thirteen-year-olds at Maker’s Yard this summer. I had a team, and your Texan friend Marc ran the opposition. We didn’t officially split boy-girl. But you know how kids are: all the boys went with good ol’ Marc and the girls with me and my pink hair.

‘Each team built three robots, and we smashed the boys! We had a robot with a hydraulic hammer. One hit and the boys’ robot disintegrated. Some of the kids were mortified, but it was worth it for the look on Marc’s idiot face.’

Charlie laughed noisily.

‘Some of the girls who were seven or eight when I first moved to Nevada are at college doing programming or engineering now. I’m really proud of that.’