Harry Brown is an elderly pensioner who is a decorated Royal Marine, and a veteran of Northern Ireland. He lives on a London council estate ruled by violent gangs and spends most of his time playing chess with his friend, Len Attwell, at a local pub owned by Sid Rourke. When the hospital phones to tell him that his wife, Kath, is dying, Harry is too late to see her because he is scared to take a shortcut through a pedestrian underpass, where a gang holds court. His wife is laid to rest next to the grave of their thirteen-year-old daughter, Rachel, who died in 1973.