I saw to my horror that thousands more were pouring into the street between us and the bridge over the river, sweeping towards us in a vast tide of flesh.

‘I think,’ said Nadia, her face shiny with perspiration and her voice trembling, ‘we’re going to have to call this one a wash. Oskar, fire off a red flare. Let the others know we’re in trouble.’

‘Seconded,’ said Oskar, grabbing hold of the flare gun once more.

‘But first,’ she said, as if to herself, ‘we’re going to have to improvise a little.’

Nadia turned the wheel, sending us down another side street. There were bee-brains here, but not in such great numbers. The map was still spread out on my knees, and by the look of things we were now definitely outside the recommended routes. I reopened the window on my side and started to pick off the fastest and strongest of the bee-brains running towards us with my rifle.

Their heads snapped back in the moment before they went tumbling to the ground and I was suddenly very, very glad for all my recent marksmanship training. They’re not human, I reminded myself, each time I looked into their blank and mindless eyes.

From behind me, Oskar cursed and muttered as he did the same thing from his side of the car.

‘Conserve your ammunition,’ said Nadia, ‘in case we really, really need it. There’s a lot more of them out there than we’ve got bullets.’

‘Something’s fucked up,’ Oskar shouted, gripping the back of Nadia’s seat with one hand and practically spitting his words in her ear. ‘We should have been able to see all this with the drones. Why the hell did they send up a white flare, when they knew there were this many bee-brains waiting for us?’

‘Shut up,’ Nadia snarled over her shoulder. ‘Soon as you’ve got a clear shot, fire that fucking flare.’

‘It’s you,’ said Oskar, turning to me now. ‘You’ve jinxed us all. Right from the beginning.’

‘Are you out of your fucking mind?’ I said.

‘Oskar?’ said Nadia, without looking around. ‘I swear to God, you will shut the fuck up right now or I will make you walk the rest of the way back. You got that?’

She swerved to avoid a tight knot of bee-brains. I pulled the map back across my lap from where it had fallen and studied it with shaking hands, tracing my finger along the length of the Pinheiros. There were multiple bridges spanning it at different points. Some looked as if they were closer than the elevated motorway Nadia had taken us across, although they were certainly a long way away from any of the designated safe routes. If we could get to one of them, maybe we could make it to the other side of the river.

I told Nadia my idea. ‘Sounds good,’ she nodded.