The Unbelievers follows evolutionary biologist Richard Dawkins and theoretical physicist Lawrence Krauss across the globe as they speak publicly to sold-out halls, advancing a thoughtful dialogue about the importance of science and reason in the modern world. Dawkins, the world's most famous atheist, and Krauss, director of the esteemed Origins Project, are dedicated to furthering the revolutionary idea that science, above all else, should inform humankind's understanding of the universe. Filmmaker Gus Holwerda follows these "rock stars of reason" as they embark on a most modern crusade to encourage people to cast off antiquated ideologies and assume a purely rational approach to important current issues. Refusing to engage with those who advance divisive and extreme fundamentalist positions, Dawkins and Krauss show how sometimes sensitive and provocative ideas can be discussed with intellectual rigour. Fans, including Ricky Gervais, Cameron Diaz, Stephen Hawking, Woody Allen and Werner Herzog, share their impressions and support, while arenas full of admirers and the curious eagerly receive them. As engaging as the subjects themselves, The Unbelievers offers an exciting glimpse into two of the world's most influential minds at work.