Based on true events, Holy Light tells the story of the first meeting of renowned journalist W.T. Stead and Welsh Revivalist Evan Roberts in 1904. Stead is something of a spiritual explorer; he believes in the spiritual realm, but has often exposed spiritual practitioners as charlatans. As is evident in his pioneering investigative work, he desires to know the truth and expose falsehoods. He hears of a religious revival which is having a huge effect on the population of south Wales. Intrigued by the references to intense Spiritual experiences he travels to Wales to report on the meetings for his newspaper. What he sees there transforms his expectation of what a spiritual experience can be. This movement is not something controlled by a medium, but something with a life of its own. When they do meet, Stead and Roberts have a lot to talk about. This inexperienced young preacher has happened upon a spiritual gift that Stead, the intrepid explorer, has been searching for his whole life. Will he let this change him, or will he go back to his old ways? The transition from darkness to light is a thematic and visual motif that will be explored throughout the film.
This story connects with the encounter between Nicodemus and Jesus, as recorded in John 3. Nicodemus is a Jewish ruler (W.T. Stead is a famous journalist, in fact he was considered the most famous British person on board the Titanic, where he lost his life 8 years later) who recognises Jesus' authority, though it confounds his world view and asks for clarification. The bible verse that Roberts quotes at Stead is exactly what Jesus says to Nicodemus. He offers him a challenge; step into the light and be right with God, or let your fear and shame keep you in darkness.