I steer the truck across town following ‘To the USA’ signs but as I turn left to the border, I realize that while getting out of the USA might have been easy, getting back in is going to be another matter entirely. Instead of empty checkpoints, hundreds of cars are backlogged into six or seven lanes, creating not only a massive gridlock but also a raging night economy to service it. Street kids are everywhere, sidling through the gaps in the lanes, tapping on car windows and offering trays of gum and noxious-looking sweets in plastic bags. Some, so grubby it looks as if their bare skin has been rubbed with a dirty tyre, advance towards the windscreen, brandishing filthy cloths and mud-streaked water buckets. Parallel to the road, Mexican soldiers carrying rifles patrol the railway with dogs. Behind them the border rises up, green and menacing into the hills. There’s an intangible crackle and sense of urgency in the air. A cripple in a wheelchair, head far too big for his wasted body, expertly manoeuvres his way through the aisles, one hand extended casually, as though money might accidentally drop into it from the Good Lord above. Street vendors offer slices of watermelon sprinkled with red chilli, bottles of Santa Maria purified water and plastic cups of Jell-O. Under the awnings of closed shops, hawkers sell garish velour towels printed with images of virgins and saints and the Last Supper. As I edge the truck into the queue, one beckons. ‘Come on, baby,’ he croons, ‘everything you like is here, I bring it over?’

I shake my head.

‘Noh?’ He grins. ‘Okay then, baby, I wait for choo all day then maybe you come back tomorrow, huh?’ I give him a thumbs-up and swiftly wind up the window just as a girl’s face appears, pale, Western-looking. Cautiously, I wind down the window again.

‘Help me,’ she begs. ‘I’ve been robbed.’ She holds up a bag with a knife slash through the bottom. ‘They took money! My passport! I can’t get across the border. I need to call the American embassy, get back to my children. Please, just a few dollars?’

It feels like a scam, but she’s an American, and in trouble, no doubt about that.

‘Look, I haven’t got a passport either,’ I say half-heartedly. ‘You could come with me.’

The girl’s eyes flick to the children. ‘Just give me some money, lady.’ She rakes her nails up and down skinny arms. An addict. I fumble in my bag and thrust a couple of dollars out of the window.

‘That it?’ Her eyes are flinty. ‘Haven’t you got more?’

I stammer an apology but she just spits on the ground and slips into the next lane.