‘But ma’am,’ he says as patiently as he can, ‘without a passport we can’t let you go home.’

At which point, all the repressed fear and frustration of the night begin to rise uncontrollably through my veins like the mercury inside Emmy’s thermometer, until finally I see red.

The man sitting behind the desk bears the faintest scars of teenage acne. His black hair is wavy and greying at the temples and he’s handsome in an old-fashioned, rakish sort of a way.

‘Yes, how many?’ He speaks quietly into the receiver. ‘Keep the men there for another hour . . . yes . . .’

Agent Harrigan herds us into the room then hastily backs out like a veterinarian assistant delivering some wild creature, a bobcat or deranged hyena, into the custody of somebody more qualified to use a stun gun. Still fired up, I’m tempted to deliver a parting snap, perhaps even sink my teeth into the beefy region of his upper arm, but I know when not to push my luck. The desk in front of us is ordered but not without personal touches. A photograph frame, a bronze statue of Degas’s ‘Little Ballerina’, a gold name slide which reads Emilio Chavez . . . and suddenly I get a sting of recognition. Of course, Chavez, the Mexican-looking official up on stage at the Ague town hall meeting.

‘No . . .’ he sighs, ‘I will speak to the family myself . . .’ He places the receiver back in its station, then presses his fingers to the bridge of his nose as if to squeeze out a headache. ‘Mrs Coleman . . .’ he begins.

‘Look—’ I say aggressively, but he holds up his hands.

‘You want to go home, I understand.’ He studies the sheet of paper on the desk. ‘Arlington Road, London.’ He looks up. ‘You’re a long way from home, Mrs Coleman.’

I nod. Tears prick my eyes.

‘This phone call concerned another young woman also a long way from home, an Ezme Santega?’ he continues conversationally, as though I might have come across her somewhere, a dinner party perhaps. ‘Ezme is an illegal immigrant who has been working in Tucson. In less than two years she earned enough money to pay a coyote fourteen hundred dollars to bring her brother across the border to join her but he never arrived. Instead the coyote contacted her and said her brother was being ransomed. She sent more money. Still he didn’t appear. She eventually sent all the money she had earned or could possibly borrow from her family, her neighbours, from other immigrants who were prepared to help. Still he didn’t appear. By the time she called us this evening, she didn’t care about being deported, she just wanted her brother back. Two hours ago, I sent men to the safe house outside Nogales where he was being held. Inside we found Kalashnikov casings and pools of blood. I very much doubt we will ever find the body of Ezme’s brother.’