Laurie Holden became famous playing the brave civil rights lawyer, Andrea, on the hit TV series The Walking Dead. But offscreen, the Canadian-raised actress recently took on the role of a lifetime.

Earlier this year, she took part in an undercover operation that resulted in the rescue of 55 sex slaves in Colombia, some as young as 12.

"I had a pretty good disguise — I had a wig and glasses," said Holden in an interview with CBC News.

Her role in the sting was to keep the young girls distracted as armed authorities closed in on their traffickers.

"We pretended we were having a big bachelor party, so my role was the girlfriend of one of the rich Americans, so I kind of had to sell them and the traffickers on the idea that I was a party girl, that I was there to have a good time with the guys."

'We have to protect those who can't protect themselves and it's not about writing a cheque.' - Laurie Holden on her work protecting victims of child sex traffickers

Holden was one of a handful of civilian volunteers who participated in the sting, orchestrated by a non-governmental organization, Operation Underground Railroad, and Colombian authorities.

They contacted Holden because they knew she had done similar work in Cambodia and Vietnam, though those were smaller operations and never involved armed personnel. 

Operation Underground Railroad is founded by the former CIA investigator Tim Ballard. It specializes in rescuing victims of child sex trafficking, often in cooperation with local authorities.  

Under Colombian laws, money must be exchanged before legal action can be taken against sex traffickers. So, Ballard and his team set up a fake bachelor party at a mansion they rented in Cartagena, Colombia.

Casting a comforting figure

Holden and another female volunteer had to gain the trust of young girls as their traffickers delivered them as "entertainment" for the party.

"When you've been sexually abused, no matter how wonderful they are, there is a fear of a man," said Holden.

"I think having myself and this other lovely woman, Krista, who is a cross-fit trainer, we were like the motherly figures who were able to comfort them."

Laurie Holden

Laurie Holden is best known for her role in AMC's horror hit, The Walking Dead. Her character Andrea was eaten by a zombie last season. (AMC)

Holden and her peers' mission was captured on undercover cameras and shown on ABC's documentary show Nightline.

Since her character on The Walking Dead was killed in the last season of the show, she's getting more scripts than ever, but the actress says the Colombian mission won't be her last.

She says her work in rescuing victims of child sex trafficking is much more meaningful. "We live in a cynical world and there's so much emphasis on money and success," said Holden. "All that fame is great but, you know, why are we here?" 

"We have to protect those who can't protect themselves and it's not about writing a cheque. That's great, but I've seen [child sex trafficking] firsthand and I can't get it out of my head, I'm just going to keep going until the day I die."

Watch Holden talk about the issue in the video above.