Was life triggered by some event, like lightning hitting a pond full of amino acids? Earth was teeming with life billions of years before the dinosaurs existed. Single celled organisms inundated the oceans, and the soil swarmed with living creatures. Where did it all come from and how do you go from a single-celled organism to a trillion-celled organism like man?

Commentator-comic Bill Maher plays devil's advocate with religion as he talks to believers about their faith. Traveling around the world, Maher examines the tenets of Christianity, Judaism and Islam and raises questions about homosexuality, proof of Christ's existence, Jewish Sabbath laws, violent Muslim extremists.