S1, E1: A night out with his girlfriend goes badly wrong when Raza Shar is arrested and identified as a potential informant for London's Counter TerrorismSpecial Unit (CTSU). Detective Sergeant Gabe Waters is partnered with new recruit DC Holly Morten and introduces her to the world of informants. Ambitious and uninhibited, Holly pushes boundaries to get Raza on board. Gabe's key contact, Yousef, has information that links to a prolific terrorist, Ahmed El Adoua.