The film, which theologian Tim Keller said moved him “to tears,” dramatizes some of the events that led to a young Lewis’ (Eddie Ray Martin) atheism — from the death of his mother to his traumatic experience in the trenches of World War I.

“Lewis lost his mother at 9 years old to cancer, had a terrible relationship with his father,” McLean said. “He saw the brutality of World War I, the butchery of it. And he came to the conclusion as a result of that, either there’s no God behind the universe, a god indifferent to good and evil, or worse, an evil god. So that was his starting point.”

The movie was filmed in 18 locations in and around Oxford, England, where Lewis was a tutor in English literature. Scenes were also filmed at his college, Magdalen, and his home, The Kilns, where he wrote his Narnia books.

The film follows Lewis as he grapples with questions of God’s existence and the impact his friends, including The Lord of the Rings author J.R.R. Tolkien, had on his faith journey.

Both scholars were “iron sharpening iron all the way through the ice,” McLean posited. He added that Tolkein appealed to Lewis’ intellect and imagination, giving him a way to understand Jesus.

“[Lewis] said … ‘If I find myself in desire that no experience in this world could satisfy, the most probable explanation is I was made for another world.’ And that other world is what he was always drawn to and helped others to see as well,” McLean said.

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Though he died in 1963, Lewis remains one of the best-known Christian authors around the world. Over the years, his fiction writings have been turned into numerous family-friendly film and TV projects, including a 1988 BBC version of The Lion, the Witch and the Wardrobe and three movies produced by Sony Pictures that grossed more than $1.5 billion worldwide.