By Stephen Weeks

I could see them coming — sweeping along, bursting through sauntering couples, like sewage from a broken pipe — a largish group, say 20. The usual loudmouth was in front, the timid ones shuffling along behind — their faces drunk-blank, jaws hanging loose. A paunchier one, shaved head and stubble beard, was wearing garter-belt and hose. I suppose he thought that was funny.

Two Nigerians had already earmarked them, stepping forward, ready to shepherd the party away. As they reached loudmouth a second team of Nigerians exchanged glances and moved in. "Free drinks at our club," they began. A slight altercation ensued with the first touts. Until this year there had been gentlemanly agreements: You see them first, they're yours. Now the competition is fiercer. Girls are now cheaper in Riga or Bucharest and so is the beer — if not quite the same quality.

They went easily down a side street, willing and foulmouthed. I was ashamed: They were my countrymen — the kind, I supposed, that had gotten off boats on the shores of India or Africa and, with no respect for local sensibilities, had won our empire long ago. Are these the kind we've got in Iraq? I hoped not. Not just the Army should have ethics lessons.

I was waiting for Mark on Wenceslas Square. At just after nine he stepped through the crowd and greeted me. We would meet the others under the Jan Hus statue on Old Town Square. Mark — determined face, Celtic coloring, dressed for hard work, with a small backpack. You'd never know he'd been through the mill himself: fostered, abused, institutionalized, including prison. Done drugs, done everything, then suddenly some Midwestern missionaries changed his life. He'd been sent abroad to do good.

The others were also American: Mark's wife and soulmate, two visitors, and Rick, who'd also kicked a lifetime of hell-raising and drugs. I had been cynical at first. But now I knew they were the right people for this job.

While the group stood in a circle, Mark led some prayers — that he and his friends were glad to be alive, and that their mission was to help those whose days had no gladness, only darkness: modern slaves, right here in kitschy-quaint, touristy Prague. If they were lucky, he said, they might just save one ... one more than God probably expected of them. Dark clouds prematurely darkened the twilight sky. I'd often wondered about the Salvation Army ... why the military ranks, the uniforms? Yet in Victorian London, there'd been similar human exploitation. Yes, then and now, a war.

We headed off toward Národní, a popular street for the dark trade. "Our work is with the girls," Mark explained. "We pass them to another charity operating a safe house. They find them work, or tickets back home — and do all the paperwork, get them new passports as their keepers have taken theirs. The house's location is a secret, even to me."

Lingering by the entrance to the metro was a young woman Mark recognized.

I was surprised she could still manage to smile. She had jet-black hair, big dark eyes, full lips — quite a catch for her captors. Mark doesn't know Bulgarian, but the girl knows some English. "Father Simon, he's from Bulgaria," Mark said. "He can obviously communicate better. They trust him more, of course."

Veneta, her real name, was wearing a skimpy dress revealing that she was very pregnant. Mark chatted until a stocky, greasy-haired man stepped out of a nearby taxi. He strode over and drew Veneta away.

"He looks after four girls here," Mark said. I suddenly noticed them, in the shadows of the buildings by the Jungmann statue.

"So who's the father?" I asked, still shocked she should be doing this while pregnant.

"Some client. But they do use condoms, except for oral."

Mark explained that her actual pimp, a Bulgarian, had been caught in a joint police operation and was now in a Sofia prison. So why was she on the streets? "Because now she sends her money to this guy in jail. She's one of these women who believe their pimp loves them. Perhaps ... they desperately hope someone cares for them."

Father Simon, a charismatic Bulgarian pastor, delivers hot soup to the women in winter with Dr. Lauren Bethell, another U.S. church activist who transferred herself here from a big UN project rescuing Thai girls from brothels. The best patch, Simon said, is on the hot vents outside the big hotels. They have to wear their skimpy costumes even when it's below zero.

"I've just run into Eva," Simon said; the small, shivering figure just inside an arcade leading into the square was pretty and was coughing into a handkerchief. "She's had oral sex with 20 or 30 men today already. Her mouth is sore. She wants to see a doctor, but they won't let her. I'll see what I can do. She knew nothing about AIDS or HIV when she was taken — and still doesn't."

Some police are transparently in the pay of major brothels, he said, but most aren't. The girls are being watched, as they're trying to catch the big fish — those running operations across Europe.

Mark told me Eva's story: only daughter of a farmer; her mother dead. A year ago a smart car arrived at their farm and out stepped two suited Russians. The dirt-poor farm would hardly provide an income for the sons and they argued to the farmer that his daughter, then barely 15, could be a liability.

They offered the father $2,000 then and there to let Eva go with them to work in Europe — in a restaurant, they said. The "advance" could be paid down from her wages. At first he wouldn't agree.

"Okay," the Russians said. "We'll come back tomorrow. That will be your last chance to accept this offer."

Overnight the father thought of $2,000. He'd never seen cash like that before. And little Eva dreamed of working in Western Europe, far better than being buried away on a farm.

The next day the bargain was sealed, and Eva found herself in a flashy car bound for Bucharest. Locked in a room, she was violently gang-raped by at least eight men. "That's their big trick," Mark said, "immediately disorientating their victim. Nothing will ever be as bad after that: Like breaking a horse, except people are kinder to animals. They broke her will."

Two weeks later she was on Prague's streets as a prostitute. A false passport got her through two frontiers, but now all her ID had been confiscated by those who bought her from the Russians. But Eva believes what they tell her: Disobey or try to escape, and the Russians will return to collect $2,000 plus interest, from her father. If he fails to pay, they'll shoot him. All the money she earns goes toward this "debt," and always will. And she is frightened to go to the police without papers.

For many of the girls — whose young bodies and pseudo-smiles hide a more terrible reality — there is no element of choice. They are, quite simply, slaves cleverly shackled, not by manacles but by threats, an invisible cage created by their keepers.

And young Eva? I won't forget her eyes. There was something dead in them, haunting me until I realized what was missing: where was her fire, her youth? That had been stolen, extinguished, killed. Like a discarded cigarette butt ground into the sidewalk.