In this ground-breaking film, historian Tom Holland explores how a new religion - Islam - emerged from the seedbed of the ancient world, and asks what we really know for certain about its rise. The result is an extraordinary detective story. Traditionally, Muslims and non-Muslims alike have believed that Islam was born in the full light of history. But a large number of historians now doubt that presumption, and question much of what Muslim tradition has to tell us about the birth of Islam. As a result, Tom finds himself embroiled in what, for 40 years now, has been an underground but seismic debate.