Sam's life changes when he comes in possession of a gun. Complicating things is the fact that his sister Gina is a police officer.

Bang is the story of a brother, a sister and a gun. Loner Sam's life is transformed when he comes into possession of a gun and starts to break the law. His ambitious policewoman sister Gina is paid to uphold it and makes it her mission to find the owner of the weapon. The family saga plays out against an inquiry into the shooting of a local businessman that raises questions for Sam and Gina about their father's murder when they were young children. A crime drama about blood, love and human relationships set in the steel town of Port Talbot.

Siblings Sam and Gina's father was murdered when they were children. Now, Gina is a police officer and Sam a criminal. Season 1 follows their family saga as the shooting of a local businessman is investigated; Sam was entrusted to look after a gun before the shooting.