On the eve of the Second World War, two of the greatest minds of the twentieth century, C.S. Lewis and Sigmund Freud converge for their own personal battle over the existence of God. The film interweaves the lives of Freud and Lewis, past, present, and through fantasy, bursting from the confines of Freud’s study on a dynamic journey.
| Actor | Role |
|---|---|
 Anthony HopkinsSigmund Freud | Sigmund Freud |
 Matthew GoodeC. S. Lewis | C. S. Lewis |
 Liv Lisa FriesAnna Freud | Anna Freud |
 Jodi BalfourDorothy Burlingham | Dorothy Burlingham |
 Jeremy NorthamErnest Jones | Ernest Jones |
 Stephen Campbell MooreJ. R. R. Tolkien | J. R. R. Tolkien |
 Orla BradyJanie Moore | Janie Moore |
 David ShieldsWeldon | Weldon |
 Tarek BisharaJacob Freud | Jacob Freud |
| GGeorge Andrew-ClarkePaddy Moore | Paddy Moore |
| GGary BuckleyAlbert Lewis | Albert Lewis |
 Pádraic DelaneyWarren Lewis | Warren Lewis |
 Rhys MannionYoung C. S. Lewis | Young C. S. Lewis |
 Anna Amalie BlomeyerIlsa | Ilsa |
 Cara ChristieClerk | Clerk |
| IIan DillonInkling (uncredited) | Inkling (uncredited) |
| JJohn HayesPriest | Priest |