The actress, who played Andrea on the hit show, is part of the volunteer-based group Operation Underground Railroad, which was founded by a former Cia agent.
She recently joined him on a covert mission to Cartagena to help rescue a group of child prostitutes and capture sex trafficker Marcus Bronschidle, according to UsMagazine.com.
The brave group's operation was caught on camera as part of a documentary called The Abolitionists.
Holden, whose job was to comfort the girls during a raid, says, "Some of them looked really terrified. I talked to a few of them and asked them how old they were. Some were 12. Some were 13. Most were 14. One of the girls came in, embraced me, started to cry, then I started to cry."