In the movie, Rylance provides the voice for the BFG (Big Friendly Giant). Based on the classic story by Roald Dahl, The BFG follows the titular character as he embarks on an adventure with a girl named Sophie. After being fearful of the BFG at first, Sophie is soon at ease when she learns that unlike the other giants, the BFG does not eat children. Together they come up with a plan to get rid of the other giants who have become increasingly bothersome.
Sophie is played by newcomer Ruby Barnhill, who Spielberg insisted is the crux of the film.
"It really came to life when Mark and Ruby stepped into their parts," he said. "That's when the movie started to live."