I will myself to think straight. Tucson. I’ll have to get her to Tucson. There’d be a hospital there, but where, in God’s name? Tucson is seventy miles away and who to ask in those deserted streets? It would be better to drive to Ague and raise help there. I sit, frozen with indecision, and then it comes to me, the thread of a memory. Ague. The town meeting. I close my eyes; see the woman with the turquoise belt buckle, hear her voice. Her two boys, problems with the bars, problems with drugs. Yes. That was it! Mexican pharmacists were no better than drug pushers. Everything was available over the counter. Pharmacies across the border were open twenty-four hours a day – and where there were pharmacies, there would be doctors.

The Arizona sky is a navy blue, speckled with diamanté. I drive carefully, stunned by how unprepared I’d been for something to go this wrong. Every few seconds I look over at Emmy. Her head is sunk onto Jack’s shoulder, her eyes still shut. At least she’s conscious, making little mewling noises at regular intervals that tear my heart in two. Oh, God, how fragile life is out here . . . Oh, God, let it not be meningitis. Let it not be a brain seizure.

Nogales, Arizona, is deserted. The motorway flies over the top of the town, but I am the only moving thing on it. Below, billboards for the Holiday Inn Express and Best Western Hotels flash by. Doggedly, I follow the big green signs for Mexico, past a Burger King, a McDonald’s, round a concrete-lined mini roundabout. I have no idea what to expect in the way of a border, but as I draw up to it I see it’s a huge official thing. Five lines of car checkpoints and customs buildings on either side. To the left traffic is creeping into the US from Mexico. I veer right. Two uniformed officials stand at one of the checkpoints talking to a truck driver, and it’s only now, right this second that it occurs to me that I do not have my passport and that I’m bound to need it, but before I have a chance to work out what to say, the car in front of me moves ahead through the barrier and I’m already winding down my window.

‘Nationality?’ the customs official asks; he casts no more than a routine eye over the children.

I gulp, say American, and I’m through.