A young college student, Josh Wheaton, finds himself at a crossroads when his philosophy professor, the skeptical and provocative Dr. Radisson, challenges him to prove the existence of God in a series of class debates. The task becomes a genuine battleground between faith and science, and Josh, who is deeply religious, is compelled to defend his beliefs before his classmates, most of whom are atheists. As the debate progresses, Josh not only faces the resistance of his professor, who is determined to dismantle any argument for God, but also the social pressure from his peers and the personal conflicts that his decision provokes in his life.
Meanwhile, the stories of other characters intertwine, who, like him, grapple with their own doubts and challenges of faith. A mother fighting to save her daughter from a dire diagnosis, a young man distancing himself from his family due to his new life, and a preacher attempting to guide those who have lost hope, all demonstrate how faith can make a difference in the darkest moments.
The film explores not just the clash of ideologies in the classroom, but also the emotional repercussions of each decision. As Josh perseveres, he becomes an icon of faith and resilience, defending his belief in a world that seems to have no place for it.