It is partially inspired by stories told to Mendes by his paternal grandfather Alfred about his service during World War I. The film takes place after the German retreat to the Hindenburg Line during Operation Alberich, and follows two British soldiers in their mission to deliver an important message to call off a doomed offensive attack. The two main roles are played by George MacKay and Dean-Charles Chapman. Mark Strong, Andrew Scott, Richard Madden, Claire Duburcq, Colin Firth, Adrian Scarborough, and Benedict Cumberbatch also star in supporting roles.