In England, retired Royal Marine Harry Brown spends his lonely life between the hospital, where his beloved wife Kath is terminally ill, and playing chess with his only friend Leonard Attwell in the Barge pub owned by Sid Rourke. After the death of Kath, Len tells his grieving friend that the local gang is harassing him and he is carrying an old bayonet for self-defense; the widower suggests him to go to the police. When Len is beaten, then stabbed to death in an underground passage, Inspector Alice Frampton and her partner Sergeant Terry Hicock are sent to investigate. They pay Harry a visit but don't have good news; the police have not found any other evidence, other than the bayonet, in order to arrest the hoodlums. This mean that should the case go to trial the gang would claim self-defense. Harry Brown sees that justice will not be granted and decides to take matters into his own hands.

Out on parole after 8 years inside Bill Hayward returns home to find his now 11 and 15 year old sons abandoned by their mother and fending for themselves. Unwilling to play Dad, an uncaring Bill is determined to move on. Although Dean the older boy has found a job and is doing his best to be a father to his younger brother Jimmy, the arrival of Bill has brought them to the attention of social services. With the danger of being put into care looming, Dean forces his feckless Dad to stay by threatening to grass him up for dealing. If there's one thing Bill doesn't want it's to go back to prison. He reluctantly agrees to stay for a week o help fool social services that the boys are being cared for. Having never really grown up himself Bill quickly connects with Jimmy and through this new bond starts to realize what he's been missing. He has a family, a place in the world. He is a father. However, their happy family set up is short lived when Jimmy gets into trouble with Bill's dangerous old cohorts. To sort it out would breach the terms of his license and risk sending him back to Jail. Bill's next steps will show what sort of a Dad he wants to be. A good one or a free one.