An extra-special finale to the series sees Scotland's favourite cops stepping up and moving on. Chief Miekelson receives a momentous phone call from London as the Met Police choose their new leader. PC Sharon McKelvie seeks wise words of advice from Desk Sergeant Karen-Anne Millar, while city cops Sarah Fletcher and Jack McLaren get their fingers on the triggers at the police firearms unit. Meanwhile, Archie Pepper uses his tech smarts to develop an app worth many millions, and a wild night at the country fair puts the spotlight on McIntosh and MacKay's chemistry as partners.