Glasgow 1975. An arson attack on a Glasgow warehouse causes the deaths of a young mother and child. Police suspect it's the latest act in a brutal gang warfare that's tearing the city apart - one that DI Duncan McCormack has been tasked with stopping. Five years ago he was walking on water as the cop who tracked down a notorious serial killer. But he made powerful enemies and when a mutilated body is found in a Tradeston slum, McCormack is assigned a case that no one wants. The dead man is wearing a masonic ring, though, and Duncan realises the victim is not the down-and-out his boss had first assumed. As McCormack looks into both crimes, the investigations are disrupted by a shocking event. A bomb rips through a pub packed with people - and a cop is killed in the blast. The cases are stacking up and with one of his own unit now dead, McCormack is in the firing line. But he's starting to see a thread - one that connects all three attacks...