The role of business in society is changing. So are our motivations as we make decisions about why and where to work.

On a recent Thursday in Manhattan, a cross-section of employees from the Sheraton Times Square met in one of the hotel’s basement conference rooms. Cooks, room attendants, cleaners, and front desk staff had all gathered for training by Marriott International, Sheraton’s parent company, on spotting the signs of sex trafficking in hotels.

According to the International Labor Organization, some 4.8 million people are trapped in forced sexual labor globally. That number includes hundreds of thousands of people in the US, the nonprofit Polaris estimates. Trafficking, the attendees learned, can happen in hotels of every type, from roadside motels to luxury boutiques.

No single image of traffickers or victims would be emblematic of the crime, the trainers explained, but researchers have identified some indicators to watch for. For instance, victims of sex trafficking—who may be any age or gender, though women are disproportionately affected—often look like they don’t belong with their party. They may arrive with minimal luggage and clothing, and they could appear intoxicated.

Among other red flags: Sex traffickers often won’t allow victims to speak for themselves, and tend to avoid contact with staff and other guests. They may ask to pay in cash, insist they don’t need housekeeping, or make excessive requests for towels.

When the short, somber PowerPoint presentation ended, the newly educated employees joined a kind of makeshift army. In a sign of how job roles are evolving as companies more pointedly embrace social causes, Marriott announced last week that it had given the same training to 500,000 employees at its many brands and franchises over the past two years.

Already offered in 17 languages, the same instructions will one day reach 700,000 people internationally—everyone who works within the Marriott universe, says Tricia Primrose, chief of global communications at the company. By the end of 2019, Marriott will also feature employee-designed awareness posters, part of a cooperation with Polaris, in public places inside the hotel.

Empowering staff, and a company’s reputation

Arguably, this form of instruction is not what the cooks, bartenders, or custodians in that room imagined would be part of their hospitality job. But the idea—training every employee to be the eyes and ears of a property—makes so much sense that one has to wonder why it hadn’t happened earlier. (While several international hotel companies have made sex-trafficking awareness training mandatory for manager or security staff, only Marriott, Hyatt, and Hilton have extended that requirement to every staff member.) Rank-and-file employees at any hotel have multiple points of contact with guests. Not only do maids enter rooms repeatedly through the day, but engineers knock on doors to fix broken heating systems or televisions, and bellhops overhear conversations in hallways and elevators.

That Marriott didn’t start its program until 2017 may have to do with how long it took businesses to reckon with sex trafficking more generally. Corporations have historically feared any association with the heinous crime, says Tu Rinsche, Marriott’s director of social impact and global responsibility. Now, however, business leaders are not only more conscious of the issue, but realize that consumers and employees hold them to the highest possible ethical standards, and reward companies seen as advocates for social justice.

Rinsche, who has previously worked on ethical sourcing and modern slave labor issues for Disney and the State Department, was hired in 2017 to spearhead this program and similar efforts to prevent forced labor at Marriott-connected construction sites. Marriott began teaching its employees about the signs of child sex trafficking in 2011, she says. It then collaborated with nonprofits ECPAT-USA and Polaris, both focused on ending sex trafficking, to design the more comprehensive research-based training material it uses today.

There is no empirical evidence that such awareness programs work. Then again, Rinsche points out, reliable data on sex traffic and its prevalence are scarce, period. Marriott does claim that more staff are now alerting managers to potential problems, and has offered some dramatic anecdotal evidence of its program’s effectiveness. In the spring of 2017, in Louisiana, a security guard at one hotel noticed a 12-year-old boy who was traveling with a pair of men. “I might take this one home tonight,” he heard one man say, according to the company’s account of the incident, so he alerted his manager, who in turn called the police. The boy, who had been kidnapped, was returned to his family.

Within weeks of that event, says Rinsche, some hotel maids in Toronto, who had also taken the training, “felt uncomfortable” around guests who had left a teenage girl in their room. Their manager investigated and contacted Toronto police. Again, it turned out that girl had been reported missing, and was being held against her will.

A ripple effect

In its training seminar, Marriott is (refreshingly) transparent about what’s at stake in a commercial sense: Though human rights are described as the first priority, one slide touched on how sex trafficking jeopardizes the hotel’s reputation and business, creating legal liabilities.

Whatever the motivation, Marriott’s staff have apparently welcomed the training. Before, “[t]here was no established protocol,” Rinsche says. When employees saw something that troubled them, but that wasn’t a clear-cut example of a crime, they “would tweet about it, take a photo, or call someone they knew.” Now they’re asked to alert a manager rather than approach a victim or suspected trafficker directly, which could put them in danger and create false positives.

Some staff are also asking if they can share the list of signs to watch for with their families, churches, or book clubs. “We are hearing from hotel workers that they’re grateful for this training,” Rinsche tells Quartz at Work. “They have no idea that this was happening in their backyard, what human trafficking was, and that there’s actually something they could do about it.”

To reach the National Human Trafficking Hotline in the US, call 1-888-373-7888, or text “BeFree” (233733). See Globalmodernslavery.org for a list of international resources.