The 32-year-old actor will play a doctor in the psychological thriller, adapted from Liz Jensen's novel of the same name, reported Deadline.
The plot follows nine-year-old Louis Drax, who suffers a near-fatal accident on his birthday. When a doctor (Dornan) starts treating the boy, he unravels a mystery that can't easily be explained by reality.
Max Minghella is behind the adapted script, and is continuing work on the project that originally began with his father Anthony before he died in 2008.
Dornan's film 'Fifty Shades of Grey' will hit theatres on on February 13, next year.