Sam Ryan looks into the death of Maggie Collins who died of a heroin overdose. Sadly, her body wasn't discovered for several days and in that time, her infant daughter died of dehydration. Soon after Maggie's death Stephen Jackson, a small-time dealer and addict, is killed in an explosion in his home. The autopsy reveals that both of them died of overdoses from the same batch of heroin and Sam begins to doubt that their deaths were accidental. When another small-time dealer is killed, the police think they have either vigilantes or a turf war on their hands. What they have is something far more complex that involves one of their own.

Are the deaths linked to a drug war or to vigilantes?

Nikki links Cats to the Lockfords via her phone and,at her flat,sees photos of her with her boy-friend Danny,whose father identifies her corpse. The police catch a man skulking at her flat,Dennis Croft,a former soldier cashiered for drug peddling who says there was a cover-up over Danny's death. At the request of Danny's parents a further post mortem is carried out,ultimately proving that he was killed by 'friendly fire'.Consequently it transpires that Lockford was not seeing Cats for sex but seeing her right financially. CCTV evidence shows that Cats' death was due to a bizarre accident but who killed the young lieutenant and why?