Hardy witnesses a shooting at his cousin Dominic's engagement party, but soon comes to realise that Dominic may know more about the incident than he is letting on. DS Shand from Operation Trident takes charge of the investigation, and begins to work on the theory that a recently formed gang, the E1s, are attempting to mark their territory to avoid their rivals, the Skens, from muscling in on their patch. When Hardy discovers his cousin has a gun, he is left feeling torn between family loyalty and his obligation to the job. As Webb and Sim speak to gang leader Mitchell Simmons in the hope of gathering further information, a second shooting leaves his girlfriend fighting for her life.