A friendship forged in 1976 between two soldiers in the turmoil of a darkened Belfast street, continues to Glasgow where both now detective officers, they find themselves investigating a batch of adulterated heroin that threatens to decimate the city's addicts. The first deaths sets two powerful and ruthless drug barons and their gangs against each, both vying for control of the drug scene. Adding to the tension is some rogue elements among the gangsters who have their own agenda's. The detectives' investigation is further complicated by some strained relationships within the police and hampered even more by an unexpected death that shocks and demoralises them both.