Nightline interviewed Kirk Cameron, who stars in the movie as a firefighter who turns to God to save his marriage, as well as Alex Kendrick--who wrote and produced Fireproof with his brother, Stephen.

"Success took more than prayers," Nightline co-anchor Terry Moran said. "It took savvy grass-roots marketing. The brothers shared their vision with pastors across the country, who then encouraged their followers to see the film."

Meyer Gottlieb--president of Samuel Goldwyn Films, which distributed Fireproof--said the Christian segment is "an under-served audience." "Hollywood is not serving that audience," he told Nightline . "It's a huge audience. I think there's great opportunities."

Nightline also interviewed Rich Christiano, producer of The Secrets of Jonathan Sperry--scheduled for theaters in September. Set in 1970, the movie stars Gavin MacLeod who mentors three boys-Jansen Panettiere, Frankie Ryan Manriquez and Allen Issacson-to follow the Lord.

Click here to watch the Nightline segment.