In the ultimate series finale, UCOS are threatened with closure following their perceived mishandling of the Henway case. Their final case begins with the bloody murder of a political activist 15 years ago at the Madhouse - a hub for people with mental health issues. Just as the team are getting somewhere, the order comes from above for Ted, Danny and Steve to cease the investigation. But in true UCOS spirit, the boys throw away the rulebook and uncover something much bigger than just a straightforward murder, involving some top officials, a multinational drugs company and signs of a massive cover-up. Danny and Fiona's relationship hangs in the balance as she must give an answer to the job offer in Aberdeen, and Sasha is pulled into a game of political cat and mouse as she realises UCOS are merely puppets in Cynthia's game.