The Responder follows Chris Carson, a morally compromised, unconventional, and crisis-stricken urgent response officer working night shifts in Liverpool. As he navigates the city's underbelly, he struggles to keep his head above water while dealing with his own mental health issues and the pressures of a failing marriage. His life becomes increasingly complicated when he is forced to take on a new rookie partner, Rachel Hargreaves, who represents the by-the-book policing he has long since abandoned. As the series progresses, Chris finds himself entangled in a dangerous web involving local drug dealers, past mistakes, and the desperate need to protect a vulnerable young girl. The show serves as a gritty, unflinching exploration of the psychological toll of frontline policing, highlighting the thin line between being a hero and a villain in a system that often feels broken.