That was one of the things her new masters were teaching her: to be a FreeSpirit was to be a flame in the wind, but not one that was attached to the wick of a candle or the top of a matchstick. Because if you needed a crutch to survive, when that crutch was gone, so were you. Extinguished.

You needed to learn to burn free. That way you could never be extinguished. Every FreeSpirit sought, one day, to become a free-floating flame in the wind.

She stared at the passing humanity on the opposite walkway. People chained to their BlackBerry emails, their iPhone keypads, their departure times, their financial worries, their guilt. Their stuff. They didn’t realize that none of it mattered. They didn’t realize that she was one of the few people on this planet who knew how to set them free.

She singled out one of the faces. A truly sad-looking man, tall and bendy, with a bad comb-over, wearing Porsche sunglasses and one of those Mandarin-collared leather jackets that were covered in motoring badges, and were designed to give off the impression that you were something important in the world of motorsport.

I could free you, she thought.

Beyond him was a group of teenagers, with backpacks, noisily teasing each other. Then her phone rang again.

Fumbling to answer it with her gloves on, she dropped it on the floor and instantly knelt down to retrieve it.

When Roy Grace looked up again from the display of his phone, the woman had gone.

Did I imagine it? he wondered. An instant ago, he was sure he had seen a woman’s hair, the same distinct, fair colour of Sandy’s hair, behind the grim-faced oldies heading rapidly towards him.

He glanced down at the display again and pressed the key to open the text message:

Yo, old-timer. At sea. Haven’t thrown up yet.

How u doing?

He composed a reply, then sent it:

Me neither.

Out of curiosity, he looked behind him. The woman with the same colour hair as Sandy had reappeared, standing behind the elderly couple, receding into the distance.

Again he felt that punch in his stomach. He turned, squeezed past a tall, irritated-looking man in a trench coat, and half walked, half ran a few steps back against the direction of the walkway. Then he wormed his way through a cabin crew group, all in uniform and towing their luggage.

Then he stopped.

Stupid.

Come on, man! Pull yourself together!

A few months ago, he might have continued to run after her, just in case…

But today he turned round and began, instead, threading a path back through the cabin crew, saying some of the few words of German he knew. ‘Entschuldigung. T’schuldigung. Danke!’

The four of them had been up all night and were cold, wet through and exhausted. On top of that, Raluca was strung out and getting increasingly agitated. She needed money, now, to go to her dealer, she told Ian Tilling.

None of the three Romanians knew what he meant when, venting his frustration, and ignoring Raluca for a moment, Tilling banged the table-top in the smoke-filled café and shouted out, ‘This is like looking for a fucking needle in a haystack!’

But they got the drift.

They were in a café, inside a corrugated-iron shack, one of a row that included a butcher’s and a mini-mart, adjoining a rubbish-strewn dirt road that was one of the main suburban arteries of Bucharest, running through Sector Four. The snow was doing a good job of tidying the street up by covering the litter.

Tilling munched hungrily on a massive, dry bread roll that had some kind of meat in the centre – he had no idea what it was. It was dead and had the consistency of leather, but it was protein. He was wired from caffeine. Ileana, Andreea and Raluca, all barely awake, were smoking. Their task was almost impossible. In a city of two million people, as many as ten thousand lived outside of society. Thousands, mostly young people, whose common currency was silence and suspicion.

For the past fourteen hours, they had scoured the sector’s shanties along the steam pipe network and they’d crawled down so many holes in the road they had lost count. But so far, nothing. No one knew Simona. Or, if they did, they were not saying.

He yawned, his tiredness bringing back memories. He’d forgotten the sheer exhaustion that came, at times, with the territory of being a police officer. The days – and nights – when you had to keep going, running on adrenalin, fuelled by the scent of progress.

It was one of the best feelings in the world.

‘Please, Mr Ian, I must go now,’ Raluca said.

‘How much do you need?’ Tilling asked her, pulling out his battered wallet.

Rubbing her thumbs anxiously together, rocking backwards and forwards on her chair and eyeing the wallet intently, as if scared it might disappear if she stopped looking at it, she said, ‘One hundred and forty lei.’ Then she picked her cigarette from the ashtray and drew hard on it.

Ian was constantly staggered at the amount of money heroin addicts needed for their fixes. This was more than she could earn in a week in a menial job. Little surprise she was a hooker. Apart from stealing or fraud, there wasn’t any other way she could earn that kind of money.

Almost beyond hope – but not beyond caring – as he riffled through the banknotes, Tilling called the proprietor over. He was an elderly, bearded man, wearing a grimy apron over brown overalls, who had lived through and survived Ceauşescu, and who seemed to have found a level of contentment with his lot, somewhere behind the resigned sadness of his expression. The former British police officer asked him whether he knew of any street kids living close by.

He knew plenty, he replied, who didn’t? Some of them came in, late afternoon, just before he closed, to scrounge any leftovers, or stale bread he was about to throw away.

‘Do you ever see a young girl and a young man together?’ Tilling asked. ‘He’s about sixteen, she’s about thirteen, but they probably look older.’ Those who lived on the streets aged fast.

There was a faint glimmer in the man’s eyes, which they all picked up on.

‘The girl is called Simona,’ Raluca said. ‘And the boy, Romeo.’

‘Romeo?’ He frowned.

Raluca, animated by the sight of the money, suddenly said, ‘You would recognize him. He has a withered left hand, short black hair, big eyes.’

The proprietor’s recognition seemed to deepen. ‘This girl with him, she has long hair? Long brown hair? Wears a multicoloured tracksuit thing – always the same?’

Raluca nodded.

‘They have a dog? Sometimes, they bring the dog in here. I find bones for him.’

‘A dog!’ Raluca became even more animated. ‘A dog! Yes, they have a dog!’

‘Some days they come here.’

‘Always when you are closing?’ Tilling asked.

‘Depends.’ He shrugged. ‘Different times, some days. Other days I don’t see them. I prefer customers!’ He laughed at his own joke. Then he said, ‘Crazy me, I’m forgetting. The girl, she was in here this morning. She asked me for a bone, for a special bone. She said she was going away and she wanted to give a bone to the dog as a goodbye present.’

‘Did she say where she was going?’ Tilling asked, panic rising inside him.

‘Yeah, I think on a cruise around the Caribbean,’ he said. Then he smiled again. ‘I ask, she didn’t tell me. Just, she said, “Away”.’

‘Do you have any idea where they live?’

He opened his arms in a shrug. ‘Close. Somewhere near to here, I think. On the street, under the street, I don’t know.’

Tilling looked at his watch. It was just gone midday. Raluca wasn’t going to be functioning well soon, without her fix, and he needed her to identify Simona and, equally importantly, to talk to her. Simona and Romeo were more likely to believe a friend than himself. But if he gave Raluca the cash, she might disappear, get her day’s supply and then crash out somewhere.