Agent Megan DiPatri took the stand and described how millionaire Bucks County businessman Andrew Mogilyansky traveled to Russia and sexually assaulted three young teenagers brought to him from an orphanage.

Even years after those violent encounters, DiPatri recounted, the girls still looked down in pain and shame while telling her how Mogilyansky stole their childhoods.

DiPatri, 41, a supervisory special agent with the U.S. Immigration and Customs Enforcement’s Philadelphia office, then watched matter-of-factly as a federal judge last week gave Mogilyansky eight years - the longest prison sentence possible under his plea agreement - plus 15 years of supervised release.

Leaving the courtroom, DiPatri showed no sign of celebration that five years of hard work had locked away another international sexual predator - the second such high-profile triumph for ICE and the U.S. Attorney’s Office in Philadelphia this year. Besides, she had paperwork to file and was eager to get her son and daughter to soccer.

That night in her South Jersey townhouse, with her children and the case both put to bed, she accomplished something that had been elusive for most of the investigation.

“I slept like a bear, finally,” DiPatri said.

Your ordinary soccer mom, she’s not.

Working on sexual tourism cases immersed DiPatri in a seamy world of international crimes against children.

UNICEF, the United Nations children’s agency, estimates that about 948,000 children are trafficked into the sexual-exploitation industry every year worldwide, including the United States.

Among the predators are tourists, often wealthy men who travel abroad to have sex with children.

Mogilyansky, a Hatboro resident, fits that profile: an entrepreneur with numerous businesses, including one that publishes the Russian Yellow Pages. A personal worth estimated at $5 million. Columbia University grad. Raised $1.2 million through his own charity to help children harmed in the 2004 Beslan school massacre in Russia.

About 25 percent of sex tourists come from the United States and Canada, according to End Child Prostitution, Child Pornography and Trafficking of Children for Sexual Purposes (ECPAT).

Sex tourism thrives on “the ease of travel and new ways of sharing information on the Internet,” said Carol Smolenski, executive director of ECPAT’s U.S. chapter.

Many sex tourists are parents who respect the law at home. Mogilyansky is the married father of three young children.

“But it feels like anything goes when they travel abroad,” Smolenski said.

When the suspect is American, Immigration and Customs Enforcement (ICE), under the Department of Homeland Security, is the main federal agency that enforces the Protect Act of 2003, which makes it illegal for a U.S. citizen to sexually exploit a child on foreign soil.

“While these types of cases are extremely challenging to investigate and prosecute, we owe it to those young victims to take action,” said Andrew M. McLees, acting special agent in charge of ICE’s Philadelphia investigations office.

Under that law, DiPatri and her colleagues investigated Anthony Mark Bianchi, 47, a former Wildwood motel owner, who was sentenced in May to 25 years for sexually molesting or attempting to molest eight young teenage boys in Eastern Europe between 2003 and 2005.

DiPatri’s skill, persistence and decency were praised by U.S. Attorney Michael Levy and Assistant U.S. Attorney Michelle Morgan-Kelly, the prosecutors in the two cases.

“A lot of agents don’t want to work these cases because they’re so emotionally taxing,” Morgan-Kelly said. “But Megan uses that to fuel her desire to bring this type of perpetrator to justice. She doesn’t shy away from the incredibly dark side of child exploitation.”

While working on the Bianchi and Mogilyansky cases, DiPatri, a single mom, was apart from her son and daughter for weeks as she traveled to Russia, Romania, and Moldova.

DiPatri, a South Jersey native, has been a Customs agent since 1992, after graduating from Rutgers University with a double major in Spanish and political science. Her parents and two of her three siblings still live in New Jersey.

She thanks God for the support of her parents.

“My parents are my rock. If I didn’t have them, I couldn’t do what I do every day,” said DiPatri.

One recent cool and rainy evening, DiPatri rushed to her parents’ house to pick up her 7-year-old son and 11-year-old daughter.

Their soccer practices were canceled. Still in work clothes and high-heeled shoes, DiPatri walked her children across a soggy field to their car, her work BlackBerry still on her waistband.

Once home, DiPatri was in high gear getting the kids ready for bed. It helps that she is well-organized - down to her bedroom bureau’s drawers, with contents neatly folded and arranged by color and function.

Chatter filled the house. DiPatri hugged her children.

The kids sort of know what their mother does for a living - tracking down bad guys. DiPatri doesn’t want them to know too much.

“She’s helping people,” DiPatri’s daughter said. “I think that’s pretty cool.”

While her children stayed and played with their grandparents, DiPatri was with boys and girls who feared that all the adults in their world might hurt them.

“As a mother, I would not want that to happen to my children or another’s children,” she said.

She shuts off those feelings when she’s on the job.

In 2008, at an office in St. Petersburg, Russia, DiPatri could tell the minute one of Mogilyansky’s victims walked in with her arms folded tight against her chest that the girl was withdrawn and scared.

She thanked the girl for coming and said something that the victim, now 18, may not have expected to hear: “I’m very sorry on behalf of the United States for what has happened to you.”

Gradually, Mogilyansky’s victim spoke - through an interpreter to DiPatri and directly to Morgan-Kelly, who is fluent in Russian.

DiPatri tried to pace the conversation according to the girl’s emotions, slowing down as the girl cried and working faster when she was calm.

“It’s their moment, it’s what’s happened to them,” DiPatri said of victim interviews. “You have to be subjective and open to it without bringing in any other feelings.”

Morgan-Kelly and DiPatri cannot talk about all the details of what Mogilyansky was accused of doing. But in Russian newspaper reports, he is portrayed as a man who liked violent sex with virgins, and who numbed his victims by giving the girls painkillers.

Mogilyansky and his supporters deny those claims, just as they reject accusations that he was part of an Internet-based prostitution ring in Russia. It was a Russian police inquiry into that ring, which turned up his name, that led U.S. authorities to investigate Mogilyansky.

Most of the evidence about Mogilyansky came from his own computer and eight hard drives that U.S. Customs and Border Protection inspectors temporarily confiscated at Philadelphia International Airport in 2004 after he returned from one of his Russian rendezvous.

DiPatri recalls Mogilyansky’s looking nonplussed when inspectors took his equipment, seemingly confident that his crimes wouldn’t be discovered.

In court last week, Mogilyansky apologized for the pain he had caused his victims, family, and friends, and promised to never again commit such crimes.

His wife, who pleaded with the judge to consider a shorter sentence for the sake of their children, watched as Mogilyansky was led away.

Despite her best efforts, DiPatri can’t always keep her two worlds from converging in her mind once in a while.

Though she is in a different unit now, the cases involving sexual predators and online child porn have prompted her to put strict rules on her kids’ Internet usage.

She has set computer bookmarks for acceptable game sites, and her daughter knows she is not allowed to surf the Internet. Her son is banned from going online by himself. No Facebook, no MySpace. Maybe never.

“You might get into a site that’s not what you think it is,” she explains to them.

“I don’t want to put the scare of death . . . on my kids,” she said, “but then again, I know what’s out there.”