Memories come back to Rebecca Bender at unexpected times. Adrenaline-producing, heart-pounding flashbacks to the time in her life when she was controlled by a sex trafficker.

Even years later, in the safety of her own family, triggers can come without warning.

“My toddler was 3 or 4, and you know, throwing a temper tantrum not wanting to go to bed. And my husband is taking her to the room like, ‘No, it’s bedtime.’ And she’s just saying, ‘Please no, please no,’” Bender says.

That everyday moment of parenting recalled her experiences from more than a decade ago.

“I started panicking. I remembered other girls being taken in the other room, hearing them begging their trafficker to stop. And I could remember being dragged into other rooms and begging him to stop. Little things like that I’m not sure I’ll ever get over.”

Bender’s experience is horrifying but not unique. There are hundreds of thousands of human trafficking victims in the U.S., estimates Polaris, a non-profit that operates the National Human Trafficking Hotline.

It's not yet clear how many victims will be identified in the law enforcement sting of illicit massage parlors in Florida that are suspected of being part of an international human trafficking ring, but several high-profile names have been charged with soliciting, including New England Patriots owner Robert Kraft, billionaire equity firm owner and prominent Republican donor John Childs and Johnny DelPrete, the longtime boyfriend of an LPGA star. They deny the charges.

The investigation has brought renewed attention to sex trafficking and prostitution, a problem that remains overlooked and misunderstood by many Americans, experts say.

“People like to think it’s a victimless crime, but that’s a myth that seems like it’s never going to die,” says Lisa L. Thompson, vice president of policy and research at the National Center for Sexual Exploitation. “Whether it’s from a situation like this – an illicit spa establishment, or engaging in prostitution by going to online sites, every man who buys sex from a woman in a brothel or any of these establishments, they have contracted out the job of violence, intimidation or coercion to a pimp or brothel owner.”

Turning a blind eye

The nature of sex trafficking, experts say, makes it not only a crime with victims but a particularly heinous one.

“Unlike most crimes which involve the buying and selling of a consumable product ... human trafficking entails the buying and selling of human beings, and they're exploited over and over again,” says Jay Albanese, professor and criminologist at Virginia Commonwealth University. “You can only sell a pile of drugs once, only sell guns once, you only sell stolen or counterfeit property once. But human trafficking you re-victimize a person every day, every hour. And I would argue that's why it's one of the most serious of all crimes.”

Survivors often describe near constant abuse that can last for years or decades.

"Can you imagine having sex with someone you don’t want to and you have to hide the disgust on your face because if you show anything other than pretending to be pleased then you’re going to blow the call, and not get the money, and if you don't get the money you’re going to be be faced with violence?" says Rebekah Charleston, a trafficking survivor who now works as a consultant and advocate for victims. "That’s what every single day is like. Over and over, every day."

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Some survivors say they had astronomical quotas to fill, and if they didn't they faced violence. One survivor told the Naples Daily News that on her first day as a trafficking victim she was forced to have sex with 21 men in six hours.

“Do about 40 at least, you don’t even reach 40,” she said her traffickers told her.

(The Daily News, a USA TODAY Network newspaper, withheld her name and some details to protect her identity, which was verified through the SWFL Regional Human Trafficking Coalition.)

Visible signs of abuse are also often present but willfully overlooked by buyers, experts say.

“I have seen a victim with a fractured arm and I ask her how long she had that issue: ‘Oh, for 2½ months,'” says Kathy Chen, a researcher for Praesidium Partners and former executive director of Asian American Community Services in Columbus, Ohio.

Charleston, who was trafficked for more than a decade after running away from home at 17, says signs are apparent even in high-end villas and luxury jets where she says she was frequently brought by traffickers.

“You're taught as someone in that world exactly what to say. It’s thinly veiled lies. ‘I’m putting myself through school,' or ‘I’m a single mom.’ Often times you’re showing up with black eyes,” Charleston says. “People are calling your phone the whole time and checking on you, obvious signs of control and abuse, yet these men don’t want to see that. They choose to ignore it.”

When she was in Las Vegas, Charleston says, it wasn’t uncommon for married men to stay at luxury resorts with their wives then go across the street to a motel and solicit women to their rooms.

“They’ll call the number in the yellow pages basically and hire a stranger to come to their room and perform whatever acts which are very degrading and oftentimes violent," Charleston says. "They begin to play out whatever role they have in their head that their wife doesn't want to do and then they go back and kiss and hug their wife like nothing happened. That is devious behavior. It's predatory-like behavior that we just expect as a society is OK because it’s just a man getting his rocks off.”

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Bender, who was trafficked from Oregon to Las Vegas when she was 19, was arrested several times in the nearly six years she was forced into sex work by a trafficker. In one of her last brushes with law enforcement, Bender says, she was at a casino ATM with a man who had solicited her when an officer approached. The officer recognized Bender.

“He's like: ‘I just arrested you in this hotel two weeks ago. You're not even supposed to be on property.’ And he grabbed me by the arm, and he said to the buyer, ‘Get out of here before you have a charge,’” Bender says. “That guy turned and left, and I got arrested for trespassing with intent to solicit. And I was being trafficked, my daughter is being held hostage at home, I was being beaten at least once a week if I didn’t bring in a quota, my trafficker was under surveillance by federal agents for an organized prostitution ring. And I went to jail. Not the buyer, the victim.”

For immigrants, vulnerability multiplied

Distrust of police is reinforced by traffickers, and it's just one of many tools they use to control victims.

For immigrants, like those in the Orchids of Asia and other spas in Florida, they're often repeatedly told from the time they get to the USA that law enforcement is corrupt, and traffickers reinforce that notion by saying they are bribing police.

Bob Houston, president and CEO of Praesidium Partners, which advocates on behalf of the anti-trafficking community, says most immigrant victims are indebted to their captors for large sums of money traffickers say they owe for bringing them into the country. Chen says she has heard of debts above $100,000.

“More often than not, the force and coercion involved is they owe a debt to the traffickers they never can repay," Houston says.

The survivor interviewed by the Naples Daily News said her first debt was $13,000. But it inexplicably increased, which experts say is another common tactic of traffickers. Once she was told she must pay 100 percent interest on what she owed every few months.

She once told her traffickers she thought she was about to pay her debt. Could she leave, find an apartment and another job?

No, one of them said: She had nearly $8,000 to pay.

“I started to cry,” she said. “Because I knew it was going to double.”

Immigrant victims often are promised high-paying jobs in the U.S. but are forced into sex work once they arrive, experts say.

“All the victims I serve, they all had a family, they all came here for a dream, the land of opportunity. This is what America is about: the land of opportunity, the freedom,” Chen says. “Their dream got distorted by people who manipulated the situation and are using them. The sad thing, I remember talking to the victims saying, ‘Did you know that you were going to do work such as this?’ And they say: ‘No, we don’t know. We don’t know anything.’”

Most can’t speak or write in English and don’t know help is available or have any way of finding it. Restore, a nonprofit organization working to end sex trafficking in New York, has found as low as 13 percent of their clients speak intermediate English, says Chris Muller, its director of training and external affairs. Enough to possibly navigate the subway but little else.

“I lived in London for a while, and I couldn't even tell you what the 911 number is,” Bender says. “How could that person leave?”

Massage parlors like prisons

At Orchids of Asia Day Spa in Jupiter, Florida, where Kraft is charged with paying for sexual services, women – many of them from China – lived in the spa and were not permitted to leave, according to Martin County Sheriff Will Snyder.

Says Thompson: “For so many women, particularly in the context of illicit prostitution and sexual servitude, they live 24/7 on premise; they may be allowed out only occasionally. They live and have to service these men where they sleep and where they cook. There’s no escape from this context: They’re basically encaged in these massage parlors.”

Charleston says similar scenarios play out even in legal brothels in Nevada where she was trafficked.

“I've seen almost every venue that this takes place in America and I've been forced to work in them all, and so I can relate," Charleston says. "Although I have not been in a massage parlor per se, it's very similar to a brothel. You know when you're captive you're inside the premises all day and customers are brought in.”

Charleston says women at Nevada brothels did not have “independent contractor” freedom to turn down buyers, describing lineups in which buyers chose women who were then required to attend them. Rooms were wired to ensure they weren’t “blowing calls,” a term for refusing or ruining the deal, or cheating management out of money.

She and other women trafficked by the same man worked 20 hour days, she says, labor-trafficked during the day at legitimate businesses and sex-trafficked at night.

Labor and sex trafficking often overlap, experts say.

At illicit spas, Muller says, the women are often running the entire business and are on call 24/7.

"They're stuck in that parlor, serving customers nonstop. If someone calls they’re expected to answer," Muller says. "Managers are watching on cameras, and they’ll be quick to respond if they feel the work isn’t being done."

The added responsibilities of maintaining the business is a control tactic, Muller says. If women are not making money to pay their traffickers, there will be repercussions.

That’s also where definitions of who is a victim and who is a manager, who could be charged with trafficking, can grow murky.

"If you're looking for black and white, it's not going to be there. When do you cross the line of becoming ... now victim and also exploiter?" Muller says.

The Florida case may raise that question as female managers are charged with prostitution as well as deriving support from the proceeds of prostitution and permitting prostitution.

Warning signs and ways out

A massage parlor may not be what people have in mind when they hear "modern-day slavery," but advocates hope this case is eye-opening to the human trafficking happening in communities large and small across the nation.

"We do not have to see handcuffs and duct tape for trafficking to exist. It does not match the stereotypes that most people have from the movies,” Bender says. "We don't have to be shackled. We're trapped due to fraud and coercion just as much as force."

The primary coercive measure is fear.

“Traffickers do all sorts of things to instill fear. They don't just threaten you, they threaten your family," Bender says.

They're met with physical abuse, which can also include sleep deprivation, food deprivation and dehydration as well as extreme isolation. Experts say some women are moved around so frequently they may not know where they are.

“We've worked with women who have been able to identify 27 different states where they've been trafficked," Muller says. "That shows the high level of movement that's associated with this. Particularly movement with a purpose, for isolation, for the purpose is disorientation."

The victim not only fears the trafficker but fears fleeing, Bender says.

“You don't know how you're going to eat. What if my family doesn't answer? What if I don't have the money to get on a plane ticket? What if I don't have my ID? How am I going to get there? What if I run out of gas?”

And victims are often given false hope that the sex work will eventually stop.

“I think traffickers are really good at dangling carrots," Bender says. "'There are other women who don't have to do it anymore. There’s the girl that runs the office. 'Now see, she started here, and now she got this great job.' You think, 'Well, I don't know how to run, and I don't quite know what to do, but if I just obey the rules a little longer I may eventually be done, too."

Truer hope is coming not only from victims advocates, but in the way the public and law enforcement have begun to recognize the role of violence and coercion in trafficking and prostitution. Bender said she's encouraged by the way the Florida women are being treated like victims.

“It's very much taken a shift in the last 10 years," she says. "Kudos to Florida law enforcement, seriously."

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If you've seen what could be human trafficking or if you need help, the National Human Trafficking Hotline 1-888-373-7888 is confidential, toll-free and available 24/7 in more than 200 languages. Text: “BeFree” (233733). Chat: humantraffickinghotline.org.

Contributing: Ryan Miller of USA TODAY, Maria Perez of the Naples Daily News