《单枪匹马 第四季》是由主演的一部欧美片，The body of elderly recluse Seamus Devlin is discovered dead in a field and the initial charge is to Ruairi, a troubled teenager, who is staying at a remote youth facility. Jack is forced to keep watch on him as he gathers evidence on the death. Meanwhile, a long-lost cousin Brian and his girlfriend Gemma opens up new wounds for Jack's mother and the discovery of an uncle Jack never knew existed - a victim of the now derelict and violent industrial school for young offenders.