Child sex trafficking is a gritty topic, but it's also a lucrative crime impacting more than 2 million children.

Singer Lexi Walker, violinist Lindsey Stirling and pianist Kendra Lowe came together to raise awareness about child sex trafficking in a touching video posted to Walker's YouTube channel Tuesday.

The trio performed an arrangement of the original song "Prayer of the Children" during a gala hosted by Operation Underground Railroad on Saturday.

Operation Underground Railroad is an abolitionist, nonprofit organization fighting child sex trafficking. Members of the organization go undercover performing sting operations to rescue children enslaved by sex traffickers.

Walker invited listeners to read more about the nonprofit organization at its website.

Watch the YouTube video here.