The central premise of Being Human is that various types of supernatural beings exist alongside human beings, with varying degrees of menace; that three of these supernatural beings are opting to live amongst human beings rather than apart from them; and that these three characters are attempting (as much as is possible) to live ordinary human lives despite the pressures and dangers of their situations. They are constantly threatened with exposure or persecution, with pressure from other supernatural creatures, and with problems caused by their attempts to deal with their own natures.

Mark Cobden is newly-imprisoned, consumed by guilt for his crime, and way out of his depth in the volatile world of prison life. Then he meets Eric McNally, an excellent prison officer doing his best to protect those in his charge.