"Sound of Freedom," directed by Alejandro Monteverde, will debut in theaters July 4 with Caviezel starring as Tim Ballard, who began his career at the CIA and then spent more than a decade as a special agent for the U.S. Department of Homeland Security battling child exploitation. Assigned to the Internet Crimes Against Children Task Force, Ballard was deployed as an undercover operative for the U.S. Child Sex Tourism Jump Team, infiltrating criminal organizations that sexually abused and trafficked children.

In 2013, Ballard and a team of former agents left DHS to form Operation Underground Railroad, a private foundation that assists international governments and U.S. law enforcement in dismantling criminal trafficking organizations that target children.

Ballard has testified before Congress on child trafficking and has advocated vigorously to raise awareness of the issue, which is estimated to affect at least 1.7 million children globally, according to the International Labor Organization.

For Caviezel, portraying Ballard -- and replicating his dramatic real-life rescues of enslaved children -- is a role second only to that of playing Jesus in "The Passion of the Christ," with a similarly compelling mission.

Ahead of the film's opening, the "Sound of Freedom" team is looking to sell "2 million tickets for 2 million children" trapped in trafficking, Caviezel told OSV News. "That's been the goal all along."

The film's distributor, Angel Studios, is using technology it developed for its hit series "The Chosen" to enable viewers to buy tickets so that others can watch for free, or to claim donated tickets if they are unable to afford the purchase price.

Both Caviezel and producer Eduardo Verástegui told OSV News that the film has been a labor of both faith and love for the past eight years.

"I was in Los Angeles and met Tim Ballard and his team -- ex-CIA agents, ex-FBI agents -- and I learned what they were doing, traveling around the world undercover, rescuing children that were kidnapped for sexual exploitation," said Verástegui. "And I was in shock. I couldn't sleep for a few days when they told me what was going on."

Verástegui said he decided to counter the problem with "a weapon of mass instruction and inspiration -- film."

Caviezel and Verástegui drew on their deeply held Catholic faith to overcome what the latter called "so many obstacles" that gave way to "so many miracles" in making the film.

"Every time I do a film, I pray the rosary and my prayer is that God would use us to really be whatever he needs us to be," said Caviezel. "In this particular case, it's a weapon against the greatest evil right now we've ever seen. And when the public really wakes up and sees this, it's going to blow their minds how wicked those people (are) that do what they do with these children."

"I pray the rosary every day," said Verástegui. "That's my biggest weapon. I go to Mass every day. … Without that, there's no way I can do what I'm doing right now."

Caviezel also prepared for filming by attending Mass and receiving the sacrament of reconciliation "to get as pure as I can in my soul," he said, admitting that researching the horrors of child sex trafficking by working with law enforcement provoked both nightmares and tears.

In addition, "fasting had to happen," said Caviezel, especially for a project that sought to expose the sexual slavery of children. "You're going to have a lot of bad demons that are not going to like that. … Scripture says some demons can only be removed by prayer and fasting."

The Holy Spirit provided inspiration for "taking and elevating" the script by Monteverde and Rod Barr into a triumphant story of good conquering evil, said Caviezel -- and without directly portraying lurid details of the film's subject matter.

In one scene, his character reviews a confiscated child pornography video to file a DHS report, but the film manages to convey the horror by instead showing only Caviezel's eye as he types up his testimony.

"The scene wasn't written that way, but … it takes you right to the edge," said Caviezel. "I needed to take it to that point, because I needed the public to understand that when Tim would come home and his children would run to him, he would literally fall on his knees and start weeping in their arms."

Verástegui said as producer he stressed the importance of "how we treat people on set," particularly the child actors.

"They never knew what this film was about," he said. "How can you explain what child pornography is to actors that are 5, 6 years old? The parents were there, and Alejandro (Monteverde) was literally protecting the integrity and the innocence of the children on set with their parents. He had that ability to tell them different stories to bring the emotions and the tears. In the editing, you see the real deal, but on set, they never knew the reality."

Ballard himself was impressed by the film's veracity, said Verástegui.

While viewing the on-set replay of the key rescue scene, the veteran operative "started crying … and broke in pieces," amazed to see his life story amplified to aid others, he said.

He and Caviezel are passionate about galvanizing the film's viewers to end child sex trafficking and enslavement.

"The power of this is that your heart gets on fire," said Caviezel. "Why does it get on fire? Because they feel the love of Jesus. … You're not afraid anymore."