‘When Veryan was pregnant with our oldest, the site manager said we were troublemakers. She grabbed Veryan and threatened to push her down the stairs leading to her office. I took photos of Veryan’s bruises, but the cops couldn’t have been less interested.’

‘Your wife could have miscarried or something,’ Charlie said, horrified.

Mango nodded, then strained as she pushed against the desk to haul herself up.

‘Do you need an arm?’ Charlie asked anxiously.

‘Could you rescue my shoes from under the desk?’

Charlie leaned under the desk and flicked two worn pool shoes, which Mango struggled to put on.

‘Everything’s swollen,’ Mango said, holding her back. ‘My feet look like footballs.’

‘When are you due?’ Charlie asked.

‘Nine weeks, and twins for my sins,’ Mango rhymed, as she headed for the door. ‘Now I know you’re more into science than cake-making. So I’d like to show you something.’

Mango held on to both handrails as she led the way down to the first floor. They rounded the end of the stairs, and Mango unlocked a door signed DEVELOPMENT KITCHEN 2.

‘Hope you can keep secrets,’ Mango said cryptically, and led the way in.

‘Is this where you …?’ Charlie asked, but was struck dumb by what she saw.

The brightly lit counter along one wall had everything you might expect of a space where cake recipes got tested: sinks, mixers, microwaves, weighing scales and metal shelving with commercial-sized tubs of icing sugar and colourings. But the opposite cabinet was obscured by some much more advanced gear, mounted on wheeled trolleys.

‘You know what this is for?’ Mango asked.

‘Gene editing,’ Charlie said, feeling tense, as she racked her brain to think what use this gear would be in a bakery. ‘Do you use genetically modified yeast?’

Mango smiled. ‘Yeast was one of the first things to be genetically modified; most bakers have been using it for more than a decade. But we buy that in big tubs, off the shelf.’

‘So …’ Charlie said, warily inspecting a large gene-sequencing machine. ‘Is this legal?’

‘For now,’ Mango said. ‘Because of SNor, Congress is rushing through legislation that will require sales and ownership of sequencing and gene-editing equipment to be registered. But, as we stand here, the only thing that’s illegal is unlicensed editing of human DNA.’

‘So you could make something like SNor, in this room, with this equipment?’

‘Easily,’ Mango said. ‘One of the scary things about synthetic viruses is that they’re relatively simple to create. I could swab samples of SNor from public restrooms all over town. Then I could alter a few genes to reshape the outer proteins and make a new SNor strain to which nobody would have immunity.

‘I’m no virus expert, but there will be websites and published scientific papers with all the technical information I’d need, and forums on the dark web where people have already posted prototypes and ideas for new SNor strains.’